Question

"Question 3 In Question 2 above, if 1 part of a red pigment requires 75mL of base, how much red pigment
should we mix with 1800 mL of base?

Class 8 Direct and Inverse Proportions Page 208"

Answer 1

Direct variation:

If two quantities increase or decrease together in such a manner that the ratio of their corresponding values remain constant, we say  that the two quantities vary  directly.

In other words x and y are said to vary directly if X/y = k , where k is a positive constant.

In direct Proportion
x/y= k

x=ky

So we can find value of k from known values, and then use the formula to calculate the unknown values

 

 Inverse variation:

Two quantities x and y are said to vary inversely or indirectly if an increase in x  causes a decrease in y and a decrease in X causes an increase in y in such a way that xy remains constant.

In other words x and y are said to vary indirectly if x y = k, where K is a positive constant.

In inverse Proportion
xy= k

x=k/y

So we can find value of k from known values, and then use the formula to calculate the unknown values

 

When two quantities x and y are in direct proportion (or vary directly) they are also written as x∝y.

When two quantities x and y are in inverse proportion (or vary inversely) they are also written as x∝ 1/y

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Solution:

[Table is in the attachment]

Let the parts of red pigment mix with 1800 ml of base be ‘x’.

 Since it is the case of direct proportion .

1/75=x/1800 

⇒75× x=1×1800 

⇒x=1×1800/75

=24 parts

Hence, with base 1800 ml 24 parts red pigment should be mixed.

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Hope this will help you...

Answer 2

1/75 =x/1800
x=24 parts