Edudel, Directorate of Education Govt. of NCT of Delhi Class 6 Mental Maths Question Bank Chapter 8 Decimals Questions Solution. In this chapter, there is total 50 math problems. We have given each questions solution step by step.
1.) Decimal form of 9/2
Multiply both numerator and denominator by 5
We get
= (9×5)/ (2×5)
= 45/10
= 4.5
2.) (i) Twelve and seven tenths.
= 12 and 7/10
= 12 + 0.7
= 12.7
(ii) Four tens seven ones and three hundredths.
= 40 + 7 + 3/100
= 47 + 0.03
= 47.03
3.)
A = 0.8, B = 1.6, C = 2.8
4.) 1m = 1/ 1000 km
120m = 120 / 1000 km
120m = 0.12km
Now 3km + 0.12 km
3 km and 120m in km using decimal = 3.120 km
5.)
7¾
7/1 × 3/4
=( 7×4 + 3×1) / 4×1
=(28 +3)/4
=31/4
= 7.75
6.) 90 + 3 + 2/10
Make all denominator same
We get
=900/10 + 30/10 + 2/10
= 932/10
= 93.2
7.) 900 + 90 + 9 + 9/10 + 9/1000
Make all denominator same
We get
= 900000/1000 + 90000/1000 + 9000/1000 + 900/1000 + 9/1000
= 99909/1000
= 999.909
8.) 200 + 5 + 7/1000
Make all denominator same
We get
= 20000/100 + 500/100 + 7/100
= 20507/100
= 205.07
9.) 4 + 3/100 + 2/1000
Make all denominator same
= 4000/1000 + 30/1000 + 2/1000
= 4032/1000
= 4.032
10.) 30 + 8/1000
Make all denominator same
= 3000/1000 + 8/1000
= 3008/1000
= 30.008
11.) 0.125 × 100
Convert decimal form into fraction form
= (125/100) × 100
= 125 /10
= 12.5 – – – ( in decimal form)
12.)
fractional form of 0.125
= 125 /1000
13.) 1.625
14.) 9.75 + 3.05 + 7.2
Convert decimal into fractionform and then make denominator same
We get
= 975/100 + 305/100 + 720/100
= 2000/100
= 20
15.) (i) 0.028 = 28/1000
= 7/250
(ii) 0.75 = 75/100
= 3/4
(iii) 0.02 = 2/100
= 1/50
16.) The place value of 4 in 12.045 = 4/ 100
Fourth hundredth.
17.) The digit at thousandth place in 753.864. = 4
18.) 78 , 8/10 , 9/100
= 78 + 0.8 + 0.09
= 78.89
19.) the sum of 12.5 + 2.35 + 0.006
Convert decimal into fraction form
= 125/10 + 235/100 + 6/1000
Make all denominator same
= 12500/1000 +2350/1000 + 6/1000
=14856 / 1000 – – – – (in fraction form)
= 14.856 – – – – ( in decimal form)
20.) 0.2 – 0.06
Convert decimal into fraction form
= (2/10) – (6/100)
Make denominator same
= 20/100 – 6/100
= 14/100 – – – – (in fraction form)
= 0.14 – – – – ( in decimal form)
21.)
x = 0.47
22.) x = 13.653
26.)
0.89 < 1.25 < 2.37 < 13.5 < 15.2
27.) 0.013 < 0.325 < 0.89 < 1.256 < 2.1
28.) 1.007 < 1.089 < 1.675 < 3.9 < 9.36
29.) 174, 17.4, 1.74, ……
Divide each new number by 10
after 1.74 Dividing it by 10 we get
174, 17.4, 1.74,0.174
30.)
31.)
32.) 33.03 > 3.34 > 3.33 > 3.3 > 3.03
33.) 45.6 > 5.5 > 5.46 > 4.56 > 0.45
34.) 44.4 > 4.444 > 4.440 > 4.04 > 0.04
35.)
(i) 6m 90cm into m
1 cm = 0.01 m
Converting cm into m
We get 6m + 0.9m
6m 90cm = 6.90m
(ii) 4210 g into kg
1 g = 0.001 kg
Converting g into kg we get
4210 g = 4210 × 0.001 kg
4120 g =4.21 kg
(iii) 80 mm into cm
1 mm = 0.1 cm
Converting mm into cm We get
80 mm = 80 × 0.1 cm
80mm = 8 cm
36.)
Value of 0.89 + (0.89 × 100) – 10
As per BODMAS rule
= (0.89 + 89) -10
= 89.89 -10
= 79.89
37.)
Value of 824 / 10 –80.1
Converting decimal into fraction form , we gett
= (824/10) –(801/10)
= (824-801)/10
= 23/10
= 2.3
38.)
Express 50 rupees 95 paise as rupees using decimal
1 paisa = 1/100 Rs
Converting paisa into rupees we get
= Rs (50 + 95/100)
= Rs (50 + 0.95)
= Rs50.95
39.)
8888 m as km using decimal.
1m = 0.001 km
Converting m into km we get
= (8888 × 0.001) km
= 8.888 km
40.)
15ml as litre using decimal.
1ml = 0.001 litre
Converting ml into litre , we get
= (15 × 0.001) litre
= 0.015 litre
41.)
Initial weight of baby Elephant = 105.85 kg
Increase in weight after 1 year = 54.95 kg
Actual weight of baby Elephant after 1 year is
= Initial weight of baby Elephant + Increase in weight after 1 year
Actual weight of baby Elephant after 1 year = (105.85 + 54.95) kg
Actual weight of baby Elephant after 1 year = 160.80 kg
42.)
Length of rope Reenuhad = 45.65 m
Rope cut into 2 pieces
Length of one rope piece = 24.89 m
Length of another rope piece =(45.65 – 24.89) m
Length of another rope piece = 20.76 metres
43.)
ABCD is a quadrilateral
Length of sides of Quadrilateral ABCD is
AB = 2.9 cm , BC = 4.5cm , CD= 5.8cm , DA= 3.8 cm
Sum of the lengths of sides of the quadrilateral = AB + BC + CD + DA
Sum of the lengths of sides of the quadrilateral = (2.9 + 4.5 + 5.8 + 3.8 ) cm
Sum of the lengths of sides of the quadrilateral =17 cm
44.)
Length of ribbon = 1.2m
Length of rope = 3.54 m longer than the ribbon.
Length of rope = 3.54 m longer than the 1.2 m
Length of rope = 3.54 m 1.2 m
Length of rope = 4.79 metres
45.)
Water hold by pail = 10.5 litres
Water hold by bottle = 8.9 litres less water than the pail.
Water hold by bottle = 8.9 litres less water than the 10.5 litres
Volume of water in the bottle = ( 10.5 – 8.9 ) litres
Volume of water in the bottle =1.6 litres
46.)
Vegetables weighing bought by Tina = 10 kg
Weight of onions = 3.250 kg
Weight of tomatoes = 2.750 kg
Weight of potatoes = Total weight of vegetables- weight of ( onions + tomatoes )
Weight of potatoes = 10 –(3.250 + 2.750) kg
Weight of potatoes = (10 –6) kg
Weight of potatoes = 4 kg
47.)
Weight of grapes = 2kg 50g
Weight of apples = 3kg 250g
Weight of Mangoes = 4kg 300g
Convert fruit Weight in kg
1g = 0.001 kg
Weight of grapes = 2kg + 0.05kg
= 2.05 kg
Weight of apples = 3kg + 0.25kg
= 3.25 kg
Weight of Mangoes = 4kg + 0.3kg
= 4.3 kg
Total weight of all the fruits (in kg) = 2.05 + 3.25 + 4.3
Total weight of all the fruits (in kg) = 9.600 kg
48.)
Total Amount Tarun has = Rs 20
Cost of Toffees bought by Tarun= Rs 15.75
Amount left with Tarun = Rs ( 20 – 15.75)
Amount left with Tarun = Rs4.25
49.)
Cost of pencil box = Rs25.50
Amount Miltali gave Shopkeeper = Rs 500
Amount Mitali got back from shopkeeper = Rs 500 –Rs 25.50
Amount Mitali got back from shopkeeper = Rs474.50
50.)
A = 2.35 and B = 1.75
value of 3A – 2B = (3×2.35) – (2×1.75)
value of 3A – 2B = 7.05 –3.5
value of 3A – 2B= 3.55
Others Chapter Solution:
Chapter 5 |
Understanding Elementary Shapes |
Chapter 6 | |
Chapter 7 |