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eSTiMATiNg THe proDuCT

We can find the estimated product by rounding off the numbers.

Example 1. Find the two estimated numbers between which the product of 48 and 4 will lie.
Solution. 48 comes between 40 and 50.
4 8
40 × 4 = 160 and 50 × 4 = 200 × 4

So, the product of 48 and 4 comes between 160 and 200. 1 9 2

Let us check: 48 × 4 = 192

Clearly, 192 lies between 160 and 200.
example 2. Find the estimated product: 73 × 26 7 0

Solution. 73 rounded off to 70 × 3 0

26 rounded off to 30 0 0
Now: 70 × 30 = 2100
+ 2 1 0 0
So, the estimated product = 2100. 2 1 0 0

Exercise 4F

1. find the two estimated numbers between which the product of the following numbers
will lie.
a. 28 × 4 b. 55 × 7 c. 64 × 3 d. 87 × 5

e. 46 × 9 f. 41 × 8 g. 44 × 6 h. 37 × 2
2. find the estimated product as well as the actual product.

a. 55 × 24 b. 28 × 13 c. 63 × 34 d. 44 × 33
e. 58 × 22 f. 42 × 24 g. 73 × 19 h. 45 × 19

WorD proBleMS

example 1. A packet contains 144 balloons. Find the number of
balloons in 24 such packets.
1 4 4
Solution. × 2 4

Number of balloons in one packet = 144
5 7 6
Number of packets = 24 + 2 8 8 0

So, the number of balloons in 24 such packets 3 4 5 6
= 144 × 24 = 3456

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Multiplication