Question

Gregory draws a scale drawing of his room. The scale that he uses is 1cm: 4ft. On this drawing, the room is 3cm long. Which equation can be used to find the actual length of Gregory's room?
A. 1/4 = x/3 C. 1/4 = 3/x

B. x/4 = 1/3 D. 1/x = 4/3

Rob chose A as the correct answer. What did he do wrong?

Answer 1

The equation can be used to find the actual length of Gregory's room is:

$\frac{1\ cm}{4\ feet } = \frac{3\ cm }{x\ feet }$

Solution:

Given that,

The scale that he uses is:

1 cm : 4 feet

On this drawing, the room is 3 cm long

Let "x" be the actual length of room

Therefore,

1 cm : 4 feet

3 cm : "x" feet

This forms a proportion. Therefore,

$\frac{1\ cm}{4\ feet } = \frac{3\ cm }{x\ feet }$

Therefore, Option C is correct

Given that,

Rob chose A as the correct answer. Which is,

$\frac{1}{4} = \frac{x}{3}$

But option A is wrong

So, Rob made a mistake in measuring the equivalent ratio, it should be $\frac{1\ cm}{4\ feet } = \frac{3\ cm }{x\ feet }$