# GMAT Math : Calculating ratio and proportion

## Example Questions

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### Example Question #21 : Calculating Ratio And Proportion

An architect built a scale model of a new building she was designing. In the scale model, the base of the building is  wide by  long. If the actual building with have base length of , what will the width of the actual building be?

Explanation:

We are asked to compare lengths of sides between a scale model and an actual building. This sounds like a ratio question. Set up our ratio so that our unknown is in the numerator. Make sure to set it up with similar sides together:

Cross-multiply and simplify to find the correct answer:

So, the width of the actual building is .

### Example Question #22 : Calculating Ratio And Proportion

Leticia ran a half marathon (13.1 miles) in  hours and  minutes. Using her average running speed, how long would it take her to run a 10k (6.2 miles)?

Explanation:

We need to use her total time and distance to find her running pace. Once we do, we can solve the problem.

That is, she ran at about a -minute-mile pace

So, it will take her about

### Example Question #23 : Calculating Ratio And Proportion

If a fabric costs  a yard, how much will  feet cost?