Page 61 - ICSE Math 4

Example 11: Es mate the product of 48 and 72. Verify the result by fi nding the actual value.
Solu on: Actual value Es mated value
5
1
4 8 5 0 (48 is rounded off to 50)
× 7 2 × 7 0 (72 is rounded off to 70)

9 6 3 5 0 0
1
+ 3 3 6 0 Mental Maths

3 4 5 6 Complete the following.

So, the es mated product is 3,500. (a) 6 × 2 × 9 = 9 × x 2
(b) 2,865 × 5 × 0 =
(c) 259 × 10 × 100 =
(d) 62 × 1,000 =

Exercise 5.7

1. Mul ply using the expanded form and verify the result by standard mul plica on.

(a) 320 × 4 (b) 653 × 8 (c) 924 × 5 (d) 876 × 7

2. Es mate the product by rounding off the numbers to the nearest 10.
(a) 49 × 83 (b) 98 × 65 (c) 114 × 28

(d) 237 × 41 (e) 108 × 175 (f) 82 × 76

3. Es mate the product by rounding off the numbers to the nearest 100.
(a) 361 × 226 (b) 472 × 594 (c) 716 × 119

(d) 453 × 249 (e) 728 × 395 (f) 205 × 145

Review Exercise

1. Construct the following tables as instructed.

(a) Table of 8 by skip coun ng (b) Table of 9 by adding 1 to 10
(c) Table of 4 by repeated addi on

2. Make a mul plica on grid for tables of 1 to 10. Then, fi nd the following products
using it.

(a) 6 × 8 (b) 5 × 3 (c) 9 × 2 (d) 8 × 8

3. Mul ply:
(a) 72 by 25 (b) 86 by 38 (c) 283 by 18

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