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Evaluate (0.42 ÷ 2.5)/(0.5 x 2.05), leaving the answer in standard form

A. 1.629 x 10^{2}

B. 1.6639 x 10^{1}

C. 1.639 x 10^{-1}

D. 1.639 x 10^{-2}

**Comments**

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First, convert decimal to fraction

0.42 = 42/100

2.5 = 2 5/10 = 25/10

0.5 = 5/10

2.05 = 2 5/100 = 205/100

For the numerator,

0.42 ÷ 2.5 = 42/100 ÷ 25/10

= 42/100 x 10/25

= 21/125

Denominator:

0.5 x 2.05 = 5/10 x 205/100

= 41/40

Therefore,

21/125 ÷ 41/40

21/125 x 40/41

= 840/5125

= 0.1639

= 1.639 x 10^{-1}

**Ans C**

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