Edudel, Directorate of Education Govt. of NCT of Delhi Class 6 Mental Maths Chapter 2 Whole Numbers Questions Solution. In this chapter, there is total 40 math problems. We have given each questions solution step by step.
1.) Determine the three consecutive whole numbers which come immediately before 17999.
Answer:0 to 10 are whole numbers
The three consecutive whole numbers which come immediately before 17999 are 17998, 17997, 17996
2.) How many whole numbers are there between 25 and 65?
Answer: the whole numbers between 25 and 65 are
26, 27, 28, 29, 30, 31, 32, 33, 34 ,35 ,36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64
So the total whole numbers between 25 and 65 is 39
3.) Find the predecessor of the smallest 3-digit number.
Answer:
Predecessor is that number which comesImmediately before the given natural number.
The smallest 3-digit number = 100
The predecessor of the smallest 3-digit number = 100 -1
The predecessor of the smallest 3-digit number is 99
4.) Find the sum of predecessor of smallest 3-digit number and successor of greatest 3-digit number.
Answer:
Predecessor is that number which comes Immediately before the given natural number.
The predecessor of the smallest 3-digit number = 100 -1
The predecessor of the smallest 3-digit number = 99
The successor of a whole number is the number obtained by adding 1 to it.
The Successor of greatest 3-digit number = 999 + 1
The Successor of greatest 3-digit number = 1000
The sum of predecessor of smallest 3-digit number and successor of greatest 3-digit number = 99 + 1000
The sum of predecessor of smallest 3-digit number and successor of greatest 3-digit number= 1099
5.) Find the product of successor and predecessor of 99.
Answer: successor of 99 is 99+1= 100
Predecessor of 99 = 99-1 = 98
The product of successor and predecessor of 99 = 100 × 98
The product of successor and predecessor of 99 = 9800
6.) Find the value of: 65×95+65×5.
Answer: As per BODMAS rule
The value of: 65×95+65×5= ((65× 95) + (65× 5))
= ( 6175 + 325)
= 6500
7.) Simplify: 169×20+169×40+169×30.
Answer:
As per BODMAS rule
169×20+169×40+169×30 = ((169×20) + (169×40) + (169×30))
= 3380 + 6760 + 5070
= 15210
8.) Find the product of: 824×4×25.
Answer: the product of: 824×4×25= 3296 × 25
= 82400
9.) What is the sum of the original number and the new number if the digits 2 and 7 are interchanged in the number 2997?
Answer:
Given number = 2997
Interchanging 2 and 7
We get number =7992
The sum of the original number and the new number = 2997 + 7992
= 10989
10.) Find the value of 1+2-3-4+5-6+7+8-9.
Answer: As per BODMAS rule
The value of 1+2-3-4+5-6+7+8-9
Separate the plus value number from minus
We get
The value of 1+2-3-4+5-6+7+8-9 = (1+2+5+7+8) – (3 + 4+6 +9)
The value of 1+2-3-4+5-6+7+8-9 = ( 23 –22)
The value of 1+2-3-4+5-6+7+8-9 = 1
11.) What should be added to (70 × 20) so that the sum is (14750 ÷ 10)?
Answer:70 × 20 = 1400
14750 ÷10 = 1475
75 should be added to (70 × 20) so that the sum is (14750 ÷ 10)
75 should be added to 1400 so that the sum is 1475
12.) Find the successor of the largest number formed by using the digit 7,3,5,4,1 only once.
Answer: the largest number formed by using the digit 7,3,5,4,1 = 75431
The successor of 75431 = 75431 +1
The successor of 75431= 75432
The successor of the largest number formed by using the digit 7,3,5,4,1 is 75432
13.) Ravi spends Rs450 on lunch and dinner. How much money he has to spend on lunch and dinner for a week?
Answer:
Amount spend per day on lunch and dinner = Rs 450
Amount spend per week on lunch and dinner = ( No. Of days in a week) × Rs 450
Amount spend 1 week on lunch and dinner = 7 days × Rs 450
Amount spend 1 week on lunch and dinner = Rs 3150
14.) Find the value of: 735+ (150 ÷ 10).
Answer: As per BODMAS rule
Solving the bracket first
We get
The value of735+ (150 ÷ 10) = 735 + 15
The value of 735+ (150 ÷ 10) = 750
15.) Find the product of largest 4-digit number and smallest whole number.
Answer: largest 4-digit number = 9999
Smallest whole number = 0
The product of largest 4-digit number and smallest whole number = 9999 × 0
The product of largest 4-digit number and smallest whole number is 0
16.) A milkman supply 50 liters of milk on Monday. The next day, he supply 40 liters of milk. If the cost of milk be Rs 75/ liter. How much did the milkman earned?
Answer: Milk supply on Monday = 50 liters
Milk supply on Tuesday = 40 liters
Total Milk supply = (50 + 40) liters
Total Milk supply = 90 liters
Cost of milk for 1 liter = Rs 75
Cost of milk for 90 liters = 90 × 75
Cost of milk for 90 liters = Rs 6750
The milkman earned total Rs 6750 for 90 liters of milk supply
17.) Find the value of: 22765 × 145 – 22765 × 45.
Answer:
the value of22765 × 145 – 22765 × 45 = (22765 × 145) – (22765 × 45)
the value of 22765 × 145 – 22765 × 45 = 3300925–1024425
the value of 22765 × 145 – 22765 × 45 = 2276500
18.) If the cost of one bat is Rs 500 and one ball is Rs 50. Then find the cost of 40 bats and 40 balls.
Answer:
Cost of 1 bat = Rs 500
Cost of 1 ball = Rs 50
Cost of 40 bats = cost of 1 bat × 40
Cost of 40 bats = Rs500 × 40
Cost of 40 bats = Rs20000
Cost of 40 balls = cost of 1 ball × 40
Cost of 40 balls = Rs 50 × 40
Cost of 40 balls = Rs 2000
The cost of 40 bats and 40 balls = Rs 20000+ 2000
The cost of 40 bats and 40 balls = Rs22000
19.) The digit 2 and 3 of a number 73024 are interchanged. Find the difference between the two numbers.
Answer: Given number is 73024
Changed number is 72034 – – – – – – (digit 2 and 3 interchanged in given number)
Difference between the two numbers = 73024 – 72034
Difference between the two numbers is 990
20.) There are 70 boxes containing 25 bottles each. If 5 more bottles were added in each box. Find the total number of bottles.
Answer:
No. of bottles in 1 box = 25 bottles
Total no. Ofboxes = 70 boxed
If 5 more bottles are added in each box
That is , Now
No. of bottles in 1 box = 25 + 5
No. of bottles in 1 box = 30 bottles
The total number of bottles = Total no. Of boxes × no. Of bottles in 1 box
The total number of bottles = 70 × 30
The total number of bottles = 2100 bottles
21.) If 66 × 12 = 792, then find the value of 660 × 120.
Answer:
If 66 × 12 = 792
Then the value of 660 × 120 = ?
Value will be same as 66 × 12 , only two more zero will be added in the answer
The value of 660 × 120 = 79200
22.) Which least number should be added to 356, to make it exactly divisible by 5.
Answer: the number which is exactly divisible by 5 ends with 0 and 5
The number 356 if added by 4 makes the value 360 , which is exactly divisible by 5
Least number should be added to 356, to make it exactly divisible by 5 is 4
23.) Which least number should be subtracted from 999 so that 33 divided the new number exactly?
Answer: the number which is exactly divisible by 33 near to 999 are 990 and 1023
990 is more close to 999
So Least number should be subtracted from 999 so that 33 divided the new number exactly = 999 – 990
Least number should be subtracted from 999 so that 33 divided the new number exactly = 9
24.) Find the product of smallest 3-digit number and its successor.
Answer : smallest 3-digit number = 100
Successor of 3-digit number = 100 +1
= 101
The product of smallest 3-digit number and its successor
= 100 × 101
= 10100
25.) Find the value of:-437 × 149 + 437 × 21 – 437 × 70.
Answer:
As per BODMAS rule
The value of 437 × 149 + 437 × 21 – 437 × 70
= (437 × 149) + (437× 21) – (437 × 70)
= (65113 + 9177) –(30590)
= 74290–30590
= 43700
26.) Find the product of largest one digit number and smallest 3-digit number.
Answer:
Largest 1 digit number = 9
Smallest 3-digit number = 100
The product of largest one digit number and smallest 3-digit number = 9 × 100
= 900
27.) How many times the digit 2 occurs in tens place in the whole numbers from 100 to 300?
Answer:
Digit 2 occurs in tens place from 100 – 200 = 10 times
Digit 2 occurs in tens place from 200 – 300 = 10 times
The digit 2 occurs in tens place in the whole numbers from 100 to 300 = 20 times
28.) Find the value of 2 × 3567 × 50.
Answer: The value of 2 × 3567 × 50
= 7134 × 50
=356700
29.) The school canteen charges Rs 20 for lunch and Rs 5 for milk each day. How much money will be charged in 8 days on these things?
Answer:
1 day lunch charge at school canteen = Rs 20
1 day milk charge at school canteen = Rs 5
8 days lunch charge at school canteen = Rs 20 × 8
= Rs 160
8 days milk charge at school canteen = Rs 5 × 8
= Rs40
In 8 days on these things money charged will be Rs 160 + Rs 40 = Rs 200
In 8 days on lunch and milk, money charged will be Rs 200
30.) Find the value of 1507 – (625/25).
Answer: the value of 1507 – (625/25)
= 1507 – 25
= 1482
31.) What is the difference between the predecessor and successor of the greatest 5-digit number?
Answer:
Greatest 5-digit number = 99999
Predecessor of the greatest 5-digit number = 9999-1
= 99998
Successor of the greatest 5-digit number = 99999 + 1
= 100000
The difference between the predecessor and successor of the greatest 5-digit number = 100000 –99998
The difference between the predecessor and successor of the greatest 5-digit number = 2
32.) What is the sum of the predecessor of 701 and successor of 299?
Answer:
The predecessor of 701 = 701-1
= 700
The successor of 299 = 299 +1
= 300
The sum of the predecessor of 701 and successor of 299= 700 + 300
= 1000
The sum of the predecessor of 701 and successor of 299 is 1000
33.) Find the value of: 3+7(5+1) ÷ 3-2.
Answer:
As per BODMAS Rule
The value of: 3+7(5+1) ÷ 3-2
= 3 + 7 (6) ÷ 3-2 – – – ( Solve the bracket first and then multiplication)
= 3 + (42 ÷ 3) -2 – – – ( solve division)
= (3 + 14) – 2 – – – ( Solve addition )
= 17 – 2 – – – ( Solve Subtraction)
= 15
34.) Find the value of: 8937 × 648 + 8937 × 122 + 8937 × 230 .
Answer:
As per BODMAS rule
The value of: 8937 × 648 + 8937 × 122 + 8937 × 230
= (8937 × 648) + (8937 × 122) + (8937 × 230) – – – ( Solve multiplication)
= 5791176 + 1090314 + 2055510 – – – ( Solve addition)
= 8937000
35.) What is the difference between the successor of the least 5-digit number and the predecessor of the greatest 3-digit numbers?
Answer:
The least 5-digit number = 10000
The greatest 3-digit number = 999
Successor of the least 5-digit number is 10000 + 1
= 10001
The predecessor of the greatest 3-digit number is 999 -1
= 998
The difference between the successor of the least 5-digit number and the predecessor of the greatest 3-digit numbers = 10001 – 998
= 9003
36.) The difference between 85 and the number obtained by reversing the digit is?
Answer:
Given Number = 85
Reversing the given number = 58
Difference between 85 and the number obtained by reversing the digit = 85 – 58
= 27
Difference between 85 and the number obtained by reversing the digit is 27
37.) By using dot (.) patterns, which smaller 2-digit number can be arranged in all the three ways namely a line, a triangle and a rectangle?
Answer:
38.) Find the value of: 24 ÷ ( 9÷3)
Answer: As per the BODMAS rule
The value of 24 ÷ ( 9÷3)
= 24 ÷ ( 9÷3) – – – – ( Solve the bracket)
24÷ ( 3 ) – – – – (Solve the division)
= 8
39.) A car driver filled his car petrol tank with 65 liters of petrol on Monday. On Tuesday, he fills the tank 35 liters of petrol. If the cost of petrol be Rs89/liter. How much did the driver spend?
Answer:
Petrol filled in car on Monday = 65 liters
Petrol filled in car on Tuesday = 35 liters
Cost of petrol per liter = Rs 89
Total petrol filled in car = petrol filled on Monday + petrol filled on Tuesday
Total petrol filled in car = 65 + 35 liters
Total petrol filled in car = 100 liters
Cost of petrol for 100 liters = 100 × 89
Cost of petrol for 100 liters = Rs 8900
The driver spend Total Rs 8900 for 100 liters of petrol
40.) Find the value of: 10 + 40 ÷ 8 × 2 – 9
Answer:
As per BODMAS rule
The value of: 10 + 40 ÷ 8 × 2 – 9
= 10 + ((40 ÷ 8 ) × 2)– 9 – – – – ( Solve division)
= 10 + ( 5 × 2) – 9 – – – – ( Solve multiplication)
= 10 + 10 – 9 – – – – (Solve addition)
=20 – 9 – – – – ( Solve Subtraction)
= 11
Also See: 6th Class Mental Maths Knowing our Numbers Questions