Tuesday , July 5 2022

# NCERT 5th Class (CBSE) Mathematics: Ratio And Proportion

### Ratio in the Lowest Terms

Of the three equal ratios 3 : 5, 6 : 10 and 9 : 15, 3 : 5 is in the lowest terms or simplest form.

We can find the simplest form of a ratio by reducing it to its lowest term just like we would do it in a fraction.

CHECKPOINT: A ratio is said to be its lowest form when the terms have an HCF of 1.

Preetam does yoga for 45 minutes every morning. His friend Subhash does yoga for 1 hour every morning.

The ration of the time that Preetam does yoga to the time that Subhash does yoga is not 45 : 1 as we cannot compare different units.

We convert 1 hour to 60 minutes and than the ratio is correctly written as 45 : 60.

45 ÷ 5 / 60 ÷  5 = 9/12 = 9 ÷ 3 / 12 ÷ 3 = 3/4

In the lowest terms we can say that the ratio is 3 : 4. That is, for every 3 minutes that is, for every 3 minutes that Preetam does yoga, Subhash does 4 minutes of yoga.

CHECKPOINT: Quantities that are being compared should be in the same units, but we do not use unit while writing ratios.

### Using Ratio

(a) Zaheeda and her friend Smita brought 35 pastries for the class party. If they had brought it in the ratio of 3 : 4, how many pastries did each bring?

Ratio of  Zaheeda’s pastries to Smita’s pastries 3 : 4

Ration of  Zaheeda’s pastries to all the pastries is 3 : 7 or 3/7

Ratio of Smita’s pastries to Zaheeda’s Pastries 4 : 3

Ratio of Smita’s pastries to all pasties is 4 : 7 or 4/7

There are 35 pastries in all.

So, Zaheeda brought 3/7 × 35 = 15 pastries.

And Smita brought 4/7 × 35 = 20 pastries.

(b) Sushmita and her brought Amar got new notebooks for the new school term in the ratio of 2 : 3. If Sushmita got new notebooks, how many notebooks did Amar get?

The ratio of Sushmita’s notebooks to Amar’s notebooks is 2 : 3 or 2/3

2 : 3 = 12 : ?

So, 2/3 = 12/?

2 × 6 / 3 × 6 = 12/18

Amar got 18 new notebooks.

## चुनौती हिमालय की 5th NCERT CBSE Hindi Rimjhim Ch 18

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