Page 237 - Start Up Mathematics_6

6. The ratio of five dozen balls to 16 balls is:

(a) 15 : 4 (b) 5 : 16 (c) 16 : 5 (d) 1 : 3
7. The third proportional to 2 and 8 is:
(a) 1 (b) 4 (c) 16 (d) 32

solve Mentally

True or False

1. The ratios a : b and b : a are equal.
2. The unit of ratio is the same as that of its terms.
3. If both terms of the ratio are multiplied by the same non-zero constant, then the ratio
remains the same.

4. If four quantities are in proportion, then the product of the first two is equal to the product of
the last two.
5. A ratio can be treated as a fraction.

Fill in the Blanks
1. In ratio a : b, the first term is known as the _____________.
2. When four quantities are in proportion, the product of the _____________ is equal to the
product of the means.

3. The second term of the ratio cannot be _____________.
4. If four quantities taken in order are in proportion then the second and third terms are known
as _____________.
5. Ratio a : b and b : a are equal only if _____________.

Answer in One Word or a Line
1. What is the ratio of 100 paise to ` 1?

2. Can we have the same ratio in different situations?
3. Can magnitude of quantities be known from their ratios?

4. When are four numbers said to be in proportion?
5. What happens to the ratio if the same non-zero number is added to both its terms?

6. What is the first and second term of a ratio known as?

let’s evaluate

1. Find x if 15 : 60 : : x : 20.
2. Find x if 20, 40, x are in continued proportion.

3. Which ratio is greater, 5 : 13 or 15 : 42?
4. An electric pole casts a shadow of length 18 m at a time when a tree 12 m high casts a shadow
9 m long. Find the height of the pole.

[Hint: Height of the pole : length of the shadow of the pole = height of the tree : length of
the shadow of the tree]

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