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JAMB Mathematics 2014 Paper

Question : 3

Total: 47

Express the product of 0.00043 and 2000 in standard form.

Solution:

Concept:

A number is in standard form when it is written as

A \times 10^n

, where

1 \le A < 10

Explanation:

Express each number using powers of

10

0.00043 = 4.3 \times 10^{-4} = 43 \times 10^{-5}

2000 = 2 \times 10^{3}

Now multiply the two numbers:

0.00043 \times 2000 = (43 \times 10^{-5})(2 \times 10^{3})

Rearrange and combine the powers of

10

= 43 \times 2 \times 10^{-5 + 3}

= 86 \times 10^{-2}

Convert

86

into standard form:

86 = 8.6 \times 10^{1}

So,

86 \times 10^{-2} = 8.6 \times 10^{1} \times 10^{-2}

= 8.6 \times 10^{-1}

Answer:

8.6 \times 10^{-1}

, which is option C.

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