Now we will learn how to solve direct variations using unitary method.

We know, the two quantities may be linked in such a way that if one increases, other also increases. If one decreases, the other also decreases.

Some situations of direct variations:

● More articles, more money required to purchase.

● More men at work, more work will be done.

● More speed, more distance covered in fixed time.

● More money borrowed, more interest to be paid.

● More working hours, more work will be done.

Solved examples on direct variations using
unitary method:

**1.** The cost of 3 kg of sugar is $ 60.
What will the cost of 8 kg of sugar be?

**Solution:**

This is a situation of direct variation, now we solve using unitary method.

Cost of 3 kg of sugar = $ 60

Cost of 1 kg of sugar = $ 60/3 = $ 20

Cost of 8 kg of sugar = $ 20 × 8

Therefore, cost of 8 kg of sugar = $ 160

**2.** If 13 books cost 169, what do 30 books
cost?

**Solution:**

This is a situation of direct variation, now we solve using unitary method.

Cost of 13 books = $ 169.

Cost of 1 book = $ 169/13 = $ 13.

Cost of 30 books = $ 13 × 30.

Therefore, cost of 30 books = $ 390.

**3.** A labourer gets $ 684 for 9 days.
How many days should he work to get $ 912?

**Solution: **

This is also a situation of direct variation, now we solve using unitary method.

For $ 684, the labourer works 9 days.

For $ 1, the labourer works 9/684 days.

For $ 912, the labourer works 9/684 × 912 days.

Therefore, for $ 912, the labourer works 12 days.

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

**7th Grade Math Problems**

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