Direct and inverse proportion

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Name – Ankit Goel Class – VIII F Roll No. – 4 Given To:- Mrs. Sandhya Khera Direct and Inverse Variation

Transcript of Direct and inverse proportion

Name – Ankit GoelClass – VIII FRoll No. – 4

Given To:-Mrs. Sandhya

Khera

Direct and Inverse Variation

Direct VariationWe have Direct Variation, if the two variables change in the same sense, that is, if one increases, so does the other.An increase or decrease in one quantity with a corressponding increase or decrease in another quantity such that the ratio remains constant is direct variation.

Direct Variation uses the following formula:

Direct Variation

Example:If y varies directly as xand y = 10 as x =2.4,find x when y = 15.What x and y go together?

Direct Variation

If y varies directly as x and y = 10find x when y = 15.

y = 10, x = 2.4make these y1 and x1

y = 15, and x = ?make these y2 and x2

Direct Variation

If y varies directly as x and y = 10as x = 2.4,find x when y = 15

Direct Variation

How do we solve this ? Cross multiply and set equal.

Direct Variation

We get: 10x = 36

Solve for x by dividing both sides by 10

We get x = 3.6

Direct Variation

Inverse VariationWhen two quantities vary inversely, an increase in one leads to the decrease in the other quantity and vice-versa, in inverse ratio.We have inverse variation if one going up causes the other to go down. An example of this might be speed and time to do a particular journey.

With Direct variation wedivide our x’s and y’s.

In Inverse variation we willmultiply them.

x1y1 = x2y2

Inverse Variation

If y varies inversely with x andy = 12 when x = 2, find y when x = 8

x1y1 = x2y2

2(12) = 8y24 = 8y

y = 3

Inverse Variation

If y varies inversely as x and x = 18When y = 6, find y when x = 8.

18(6) = 8y 108 = 8y y = 13.5

Inverse Variation

The End!