National Occupational Competency Testing Institute (NOCTI) Cosmetology Practice Exam

In a tint formula where the ratio of shade A to shade B is 3:1, this means for every 3 parts of shade A, there is 1 part of shade B. Given that 1-1/2 oz. of shade A is used, we can determine the amount of shade B required by first expressing 1-1/2 oz. of shade A in terms of a single part.

The total parts in this ratio are 3 parts of A plus 1 part of B, making 4 total parts. If 1-1/2 oz. represents the 3 parts of shade A, we can find the size of a single part by dividing 1-1/2 oz. by 3.

Calculating this, we have:

1-1/2 oz. = 1.5 oz.

1.5 oz. ÷ 3 = 0.5 oz. (this is the value of 1 part)

Since shade B represents 1 part in the ratio, the amount of shade B needed will be equal to 0.5 oz. Therefore, when using 1-1/2 oz. of shade A in a 3 to 1 ratio