We will learn how to solve problems on unitary method using direct variation.

We know, if two quantities are related in such a way that the increase in one quantity results in a corresponding increases in the other and vice versa, then such a variation is called a direct variation.

Solved problems on unitary method using direct variation:

**1.** A lobour get $980 for 14 days work. How many days should he work to get $2100?

**Solution:**

This is also a situation of direct variation as money is received for working more days.

$980 is earned by a labour in 14 days.

$1 is earned by a labour in 14/980 days.

$2100 is earned by a labour in 14/980 × 2100 days.

Therefore, $2100 is earned by a labour in 30 days.

**2.** If 4 men and 5
women can earn $480 in a day, find how much 9 men and 11 women will earn in a
day?

**Solution:**

This is a situation of direction variation.

More men can earn more in a day.

In a day 4 men can earn $ 480

1 men can earn $480/4 and 9 men can earn $480/4 × 9 = $1080

Also, 5 women can earn $ 480 and 1 woman can earn $ 480/5 = $96

11 women can earn = $ 96 × 11 = $1056

Therefore, 9 men and 11 women can earn $(1080 + 1056) = $ 2136

**3.** A car travels 360 km in 60 liters of
petrol. How much distance will it cover in 12 liters of petrol?

**Solution: **

This is also a situation of direct variation.

Less quantity of petrol, less distance covered.

In 60 liters of petrol, distance covered = 360 km.

In 1 liter of petrol, distance covered = 360/60 km.

In 12 liters of petrol, distance covered = 360/60 × 12 km

Therefore, in 12 liters of petrol, distance covered = 72 km.

Situations of Direct Variation

Situations of Inverse Variation

Direct Variations Using Unitary Method

Direct Variations Using Method of Proportion

Inverse Variation Using Unitary Method

Inverse Variation Using Method of Proportion

Problems on Unitary Method using Direct Variation

Problems on Unitary Method Using Inverse Variation

Mixed Problems Using Unitary Method

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