Evaluate: \;0.42 ÷ 2.5/0.5 × 2.95, leaving the answer in the standard form.

Correct Answer is : 1.639 x 10−1^{-1}−1

Correct Answer is : 1.639 x 10−1^{-1}−1

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WAEC Mathematics 2019 Paper

Question : 50

Total: 50

Evaluate:

\;\frac{0.42 \div 2.5}{0.5 \times 2.95}

, leaving the answer in the standard form.

Solution:

Concept:

A fraction is simplified by evaluating the numerator and denominator separately.

Standard form is written as

a \times 10^n

, where

1 \le a < 10

Explanation:

Simplify the numerator:

0.42 \div 2.5 = 0.168

Simplify the denominator:

0.5 \times 2.05 = 1.025

Divide the results:

\frac{0.168}{1.025} = 0.1639...

To express

0.1639...

in standard form, shift the decimal point one place to the right.

0.1639... = 1.639... \times 10^{-1}

Therefore, the value in standard form is

1.639 \times 10^{-1}

Answer:

Option C.

1.639 \times 10^{-1}

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