1. Knowing Our Numbers Worksheet With Answers Page 19
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25(c) 67,983 – 23,865
Let’s round off to the nearest thousands.
68,000
67,983 is rounded off to 68,000.
– 24,000
23,865 is rounded off to 24,000.
44,000
Therefore, estimated difference = 68,000 – 24,000
= 44,000
However, actual difference = 67,983 – 23,865
67,983
= 44,118
– 23,865
On rounding off 44,118 to its nearest thousands, it
44,118
becomes 44,000.
Therefore, estimation is quite reasonable.
Example 29: Estimate each of the following products by rounding off each number to its nearest
hundreds:
(a) 377 × 432
(b) 245 × 598
Solution:
(a) 377 × 432
Rounding off each number to the nearest hundreds:
377 its rounded off to 400.
432 is rounded off to 400.
Therefore, estimated product = 400 × 400 = 1,60,000
(b) 245 × 598
Rounding off each number to the nearest hundreds:
245 is rounded off to 200.
598 is rounded off to 600.
Therefore, estimated product = 200 × 600 = 1,20,000
Example 30: Find the estimated quotient for (a) 477 ÷ 19
(b) 862 ÷ 29
Solution:
(a) 477 ÷ 19
Do you know?
Rounding off each number to the greatest place:
477 rounded off to the nearest hundreds is 500.
12 inches
= 1 foot (ft)
19 rounded off to the nearst tens is 20.
3 feet
= 1 yard (yd)
1 decade
= 10 years
Therefore, estimated quotient = 500 ÷ 20 = 25
10 decades = 1 century
(b) 862 ÷ 29
Rounding off each number to the greatest place:
862 rounded off to the nearest hundreds is 900.
29 rounded off to the nearst tens is 30.
Therefore, estimated quotient = 900 ÷ 30 = 30
Exercise 1.3
1. Estimate each of the following sum to its nearest tens:
(a) 67 + 40
(b) 78 + 43
(c) 881 + 728
(d) 567 + 432
2. Estimate each of the following sum to its nearest hundreds:
(a) 367 + 564
(b) 872 + 569
(c) 852 + 769
(d) 5,139 + 7,653
19
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