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Exercise 3E

1. Find the product using the lattice multiplication method.

a. 35 × 4 = ______ b. 53 × 7 = ______ c. 43 × 8 = ______
d. 134 × 5 = ______ e. 246 × 8 = ______ f. 372 × 6 = ______

g. 4126 × 3 = ______ h. 2343 × 6 = ______ i. 1783 × 9 = ______

2. Multiply the following using the lattice multiplication method.

a. 43 × 26 b. 53 × 73 c. 84 × 29 d. 86 × 54
e. 246 × 34 f. 543 × 67 g. 298 × 93 h. 2563 × 37

ESTiMATinG THE ProDuCT

We have already learnt about rounding off numbers and finding the estimated sum
as well as difference. The same concept can be used to find the estimated product.

Example 1. Find the estimated product as well as the actual product of 56 and 24 by
rounding each number to the nearest 10.

Solution. 56 rounds up to 60, and 24 rounds down to 20.
Therefore, estimated product = 1200 and actual product = 1344.

Estimated product Actual product

Th H T O Th H T O
6 0 5 6
× 2 0 × 2 4

1 2 0 0 1 3 4 4

Example 2. Find the estimated product as well as the actual product of 507 and 145
by rounding each number to the nearest 100.

Solution. 507 rounds down to 500, and 145 rounds down to 100.

Therefore, estimated product = 50000 and actual product = 73515.
Estimated product Actual product

TTh Th H T O TTh Th H T O

5 0 0 5 0 7
× 1 0 0 × 1 4 5

5 0 0 0 0 7 3 5 1 5

54 Mathematics 4