Page 34 - ICSE Math 4

Step 3: Add the hundreds including the 1 carried over. Th H T O
1 1
1 + 3 + 2 = ? ? 3 8 4
1 + 3 + 2 = 6
+ 6 2 5 7
So, write 6 in the blank space under the
hundreds column. 8 6 4 1
Step 4: Look at the thousands column.
Th H T O
? + 6 = 8 1 1
2 3 8 4
8 is more than 6.
Thus, 8 – 6 = 2 + 6 2 5 7

(sum – one addend = other addend). 8 6 4 0
So, write 2 in the blank space.

Estimating the Sum

We know that es ma on gives an approximate value of the sum. We can round off a
number to any place depending upon the degree of accuracy required.
To es mate the sum, round off the given addends to the nearest 10; 100; 1,000; etc., and

then add.
Example 6: Es mate the following sums by rounding off the addends as men oned.

(a) 243 + 1,654 + 2,285 (to the nearest 10)
(b) 3,456 + 2,461 + 5,428 (to the nearest 100)

(c) 1,045 + 6,781 + 4,382 (to the nearest 1,000)

Solu on: (a) 240 + 1,650 + 2,290 = 4,180 (b) 3,500 + 2,500 + 5,400 = 11,400
(c) 1,000 + 7,000 + 4,000 = 12,000

Exercise 3.3

1. Add the following numbers using the expanded form.
(a) 5,325 + 784 (b) 5,637 + 2,983 (c) 6,845 + 2,930 (d) 3,620 + 2,048

2. Find the missing digits.

(a) Th H T O (b) Th H T O

4 ? 6 ? 2 4 ? 2

+ ? 6 ? 8 + 4 ? 9 ?

7 2 0 1 ? 2 4 8

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