Test Index

BECE Mathematics 2010 Paper

Question : 35

Total: 40

Solution:

Concept:

In an enlargement, the scale factor is constant for all pairs of corresponding sides.

Explanation:

Let the unknown side of Fig. II be

EF

Using the corresponding sides

F'G'

and

FG

, the scale factor is:

\text{Scale factor} = \frac{20\,\text{cm}}{5\,\text{cm}} = 4

The same scale factor relates

E'F'

EF

\frac{E'F'}{EF} = \frac{12\,\text{cm}}{EF} = 4

Cross multiply to get:

12 = 4 \times EF

Divide both sides by 4:

EF = \frac{12}{4} = 3\,\text{cm}

Answer:

EF = 3\,\text{cm}

, so the correct option is D.

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