We will learn the basic knowledge for estimating a sum. Here we will learn an easy way to estimate a sum of two numbers by rounding.

In case of two digit numbers we can only round the number to the nearest tens place i.e. only one place estimate.

** For example,** let us estimate the following sums:

(i) 47 + 32

We need to round the number to the nearest 10.

47 → 50

32 → 30

50 + 30 = 80

(ii) 25 + 34

We need to round the number to the
nearest 10.

25 → 30

34 → 30

30 + 30 = 60

(iii) 75 + 13

We need to round the number to the nearest 10.

75 → 80

13 → 10

80 + 10 = 90

**1.** Estimate the sums of 72 and 48

**Solution:**

We round the number to the nearest 10.

72 → 70

48 → 50

So, 72 is nearest to 70 and 48 is nearest to 50

70 + 50 = 120

**Thus
the estimated sum = 120**

**2.** Estimate the sums to the nearest ten and also find the actual sum
of 87 and 79.

**Solution:**

We round the number to the nearest 10.

87 → 90

79 → 80

So, 87 is nearest to 90 and 79 is nearest to 80

90 + 80 = 170

**Thus
the estimated sum = 170**

** **

The actual sum of 87 and 79

87 + 79 = 166

**Thus
the actual sum = 166**

**Note: **To estimate to the nearest 10,
we see the digit/number at one’s place. It is converted to 0 or 10 as proper.
If the digit/number is < 10/2, it is converted to zero and if it is >
10/2, it is converted to10.

In case of three digit numbers we can only round the number to the nearest tens place i.e. only one place estimate.

**For example**, let us estimate the following
sums:

**1.** Estimate the sums of 586 and 120

**Solution:**

We round the number to the nearest hundred.

586 → 600

120 → 100

So, 586 is nearest to hundred is 600 and 120 is nearest to hundred 100

600 + 100 = 700

**Thus
the estimated sum to nearest hundred** **= 700**

We round the number to the nearest tens.

586 → 590

120 → 120

So, 586 is nearest to ten is 590 and 120 is nearest to hundred 120

590 + 120 = 710

**Thus
the estimated sum to nearest ten** **= 710**

**From Estimating a Sum to HOE PAGE**

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