Question

Newer stocks can be bought for $8 each, while older stocks can be bought for $4 each. The total cost, in dollars, of 10 stocks is represented by the expression 8s+4(10-s), where s represents the number of new stocks bought. how does changing the value of s change the value of the term 4(10-s)?
A.) For values of s less than 10, the term 4(10-s) will be negative; for values of s greater than 10, the term will be negative; for values of s equal to 10, the term will equal 0.

B.) For values of s less than 10, the term 4(10-s) will be negative; for values of s greater than 10, the term will be positive; for values of s equal to 10, the term will equal 0.

C.) For values of s less than 10, the term 4(10-s) will be positive; for values of s greater than 10, the term will be positive; for values of s equal to 10, the term will equal 0.

D.) For values of s less than 10, the term 4(10-s) will be positive; for values of s greater than 10, the term will be negative; for values of s equal to 10, the term will equal 0.

Answer 1

The correct option is D.
The equation given in the question is 8S + 4[10 -S], where S is the number of new stock bought.
Changing the value of S in the 4[10 - S] component of the equation will change the equation. To get the the correct option you have to considered individually all the options given in the question.
Let consider option D.
For value of S less than 10, the term will be positive. For instance, let use 6.
4 [10 - 6] = 16.
For value of S greater than 10 the value will be negative. For instance, let use 20.
4 [10 - 20] = - 40.
For value of S equal to 10, the value will be zero. For instance, let S = 0
4[10 - 10] = 0.