Find the quantity indicated.
-y varies directly as z. If y = 110 when z = 11, find y when z = 13.
A) y = 121
B) y = 130
C) y = 100
D) y = 169

Question

Quizplus · Accepted Answer

If y varies directly as z, then y = kz, where k is the constant of variation. 
To find k, we can use the given information: 
y = 110 when z = 11 
110 = k(11) 
k = 10

Now we can use this value of k to find y when z = 13: 
y = kz 
y = 10(13) 
y = 130

Therefore, y = 130 when z = 13. The best choice is B. If y varies directly as z, then we can write y = kz for some constant k. 
To find k, we can use the given information that y = 110 when z = 11:
110 = k(11)
k = 10
Now we can use this value of k to find y when z = 13:
y = 10(13) = 130

Find the Quantity Indicated