## Chapter 5 Decimal Fractions Set 5.4

Question 1.

Carry out the following divisions.

i. 4.8÷2

ii. 17.5÷5

iii. 20.6÷2

iv. 32.5÷25

Solution:

i. 4.8÷2

ii. 17.5÷5

iii. 20.6÷2

iv. 32.5÷25

Question 2.

A road is 4 km 800 m long. If trees are planted on both its sides at intervals of 9.6 m, how many trees were planted?

Solution:

Length of road = 4 km 800 m

= 4 × 1000 m + 800 m

= 4000 m + 800 m

= 4800 m

Number of trees on one side = 4800 ÷ 9.6

= 500

∴ Number of trees on both sides = 2 x number of trees on one side

= 2 x 500 = 1000

If the trees are planted at the beginning of the road, then

Total number of trees = 1000 + 2 = 1002

∴ Total number of trees planted is 1000 or 1002.

Question 3.

Pradnya exercises regularly by walking along a circular path on a field. If she walks a distance of 3.825 km in 9 rounds of the path, how much does she walk in one round?

Solution:

Total distance walked in 9 rounds = 3.825 km

∴Distance walked in 1 round = 3.825 4 ÷ 9

= 0.425 km

∴ Total distance walked in 1 round is 0.425 km.

Question 4.

A pharmaceutical manufacturer bought 0.25 quintal of hirada, a medicinal plant, for Rs 9500. What is the cost per quintal of hirada? (1 quintal = 100 kg)

Solution:

Cost of 0.25 quintal of hirada = Rs 9500

∴ Cost of 1 quintal of hirada = 9500 ÷ 0.25

= Rs 38,000

∴ Cost per quintal of hirada is Rs 38,000.

**Intext Questions and Activities**

Question 1.

Maths is fun! (Textbook pg. no. 34)

- Consider any three-digit number (say 527).
- Multiply the number by 7. Then multiply the product obtained by 13, and this product by 11.
- The found product is 5,27,527.

Take two or three other numbers. Do the same multiplication and find out how it is done.

Solution:

7 × 13 × 11 = 1001

∴ 527 × 1001 = 527 × (1000+ 1)

= (527 × 1000) + (527 × 1)

= 527000 + 527 = 527527

Thus, when any three-digit number is multiplied with 1001, the product obtained is a six-digit number in which the original three-digit number is written back to back twice.

(Students may consider any other three-digit numbers and verify the property.)