If 4956 × 25 = 123,900, evaluate 495.6 × 2.5 leaving the answer in standard form.

Correct Answer is : 1.239×1031.239 × 10³1.239×103

Correct Answer is : 1.239×1031.239 × 10³1.239×103

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BECE Mathematics 2013 Paper

Question : 26

Total: 40

4956 \times 25 = 123,900

495.6 \times 2.5

Solution:

Concept:

Use place value to rewrite the given factors and then express the result in standard form.

Explanation:

Note that

4956 = 495.6 \times 10

and

25 = 2.5 \times 10

Substitute these into the given product:

495.6 \times 10 \times 2.5 \times 10 = 123900

This means:

495.6 \times 2.5 \times 100 = 123900

Divide both sides by

100

to isolate

495.6 \times 2.5

495.6 \times 2.5 = \frac{123900}{100} = 1239

Now write

1239

in standard form.

Move the decimal point three places to the left, so

1239

becomes

1.239

Multiply by

10^{3}

to keep the value unchanged:

495.6 \times 2.5 = 1.239 \times 10^{3}

Answer:

1.239 \times 10^{3}

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