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WAEC Mathematics 2019 Paper

Question : 4

Total: 50

^2

^2

Solution:

Concept:

Use the algebraic identity for the difference of two squares:

a^2 - b^2 = (a + b)(a - b)

Explanation:

Let

a = 27.63

and

b = 12.37

First, add the two numbers:

a + b = 27.63 + 12.37 = 40.00

Next, subtract the two numbers:

a - b = 27.63 - 12.37 = 15.26

Now apply the identity:

(27.63)^2 - (12.37)^2 = 40.00 \times 15.26 = 610.4

Round

610.4

to three significant figures.

The fourth digit is

4

, which is less than

5

, so the first three digits remain unchanged.

Thus,

610.4 \approx 610

Answer:

D. 610

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