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JAMB Mathematics 2014 Paper

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Question : 5

Total: 47

If log7.5 = 0.8751, evaluate 2 log75 + log750

6.6252
6.6253
66.252
66.253

Solution:

Concept:

Use logarithm laws to express

75

and

750

in terms of

7.5

.

Explanation:

Given

\log 7.5 = 0.8751

.

Since

75 = 10 \times 7.5

, we have:

\log 75 = \log 10 + \log 7.5 = 1 + 0.8751 = 1.8751

Since

750 = 100 \times 7.5

, we have:

\log 750 = \log 100 + \log 7.5 = 2 + 0.8751 = 2.8751

Now substitute into the expression:

2\log 75 + \log 750 = 2(1.8751) + 2.8751

= 3.7502 + 2.8751

= 6.6253

Answer:

6.6253

Correct option: B

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