SChand Composite Mathematics Class 7 Chapter 3 Decimals Exercise 3D

 Exercise 3D

Question 1

Convert 

(i) 8 km to m

=8×1000 m

=8000 m

(ii) 4.8 hg to cg

=4.8×10000 cg

=48000 cg

(iii) 18.5 L to ml

=18.5×1000

=18500 ml

(iv) 23.35 dl to cl

=28.35×10 cl

=283.5 cl

(v) 93 dag to dg

=93×100 dg

=9300 dg

(vi) 29.83 hm to m

=29.83×100 m

=2983 m

(vii) 9600 mm to m

$=9600 \times \frac{1}{1000}$ m

=9.6 m

(viii) 32.48 dag to kg

$=32.48 \times \frac{1}{100}$

=0.3248 kg

(ix) 125 cm to dam

$=125 \times \frac{1}{1000}$

=0.125 dam

(x) 292 ml to cl

$=292 \times \frac{1}{10}$

=29.2 cl

(xi) 179.6 dg to hg

$=179.6 \times \frac{1}{1000}$

=0.1796 hg

(xii) 0.85 dal to cl

=0.85×1000 cl

=850 cl

(xiii) 750 m to km 

$=750 \times \frac{1}{1000}$

=0.75 km

(xiv) 1600 ml to l

$=1600 \times \frac{1}{1000}$

=1.6 l

(xv) 8.75 kg to g

=8.75×1000 g

=8750 g

Question 2

Convert :

(i) 46 m 18 cm to cm

=46×100 cm + 18 cm 

=4600 cm + 18 cm

=4618 cm

(ii) 1 kg 2g to g

=1×1000 g + 2 g

=1000 g + 2g

=1002 g

(iii) 6 km 350 m to m

=6×1000 m + 350 m

=6000 m + 350 m

=6350 m

(iv) 3749 m to km and m

=3000 m + 749  m

$=3000 \times \frac{1}{1000}$ km + 749  m

=3 km 749 m

(v) 349 cl to l and cl

= 300 cl + 49 cl

$=300 \times \frac{1}{100}$ l + 49 cl

=3 l 49 cl

(vi)  5003 g to kg and g

= 5000 g + 3 g

$=5000 \times \frac{1}{1000}$ kg + 3 g

=5 kg 3 g

(vii) 6095 mg to g and mg

= 6000 mg +  9 5   mg 

$=6000 \times \frac{1}{1000}$g+95 mg

=6g 95 mg

(viii) 2302 cm to m and cm

=2300 cm + 2 cm

$=2300 \times \frac{1}{100}$ m + 2 cm 

=23 m 2 cm

(ix) 18 km 5 m to m

=18×1000 m + 5 m

=18000 m + 5 m 

=18005 m

 (x) 5 kl 250 l to l 

=5000 l + 250 l 

=5250 l

Question 3

The Mariana Trench is about 10,900 m deep in the pacific Ocean . Is this greater or less than 8.85 km height of Mt.Everest.

Sol :

Mariana Trench is greater because height of Mt.Everest 8.85×100 m=8850 m

=10900-8850

=2050 m greater

Question 4

The thickness of 54 sheets of paper is 15.12 mm.What is the thickness of each sheet in cm?

Sol :

15.12 mm into cm $=15.12 \times \frac{1}{10}$ cm

=1.512 cm

Thickness of 54 sheets=1.512 cm

Thickness of 1 sheet$=\frac{1.512}{54}$

=0.028 cm 

Question 5

An inch contains 2.54 cm. How many cm will be in 12.5 inches?

Sol :

If 1 inch contains 2.54 cm

∵cm in 12.5 inches=2.54×12.5

=31.75 cm

Question 6

Gauri spends 0.75 of her salary every month. If she earns 12000 per month in how many month will she save 39000 ?

Sol :

Gauri Save=1-0.75

=0.25 of the salary

=0.25×1200=3000

Gauri save 3000 per month

∴She will save 3900 in $=\frac{39000}{3000}$=13 month

Question 7

How many jars each holding 1.75 kg of jam can be filled from a vessel containing 100 kg of jam and how much remains?

Sol :

Each jars contains=1.75 kg jam

So from 100 kg vessel fill $=\frac{100}{1.75}=\frac{100 \times 100}{1.75}$

$=\frac{400}{7}$

=57 jars will filled

and $\frac{1}{7}$  of 1.75 is left remains