If y varies directly with x , and if when , find y when x is 15.
A) 64
B) 60
C) 4
D) 35
E) 3.75

Question

If y varies directly with x , and if  when  , find y when x is 15.
A) 64 
B) 60 
C) 4 
D) 35 
E) 3.75

Quizplus · Accepted Answer

Let's use the formula for direct variation:

y = kx

where k is the constant of variation.

We know that when x = 11ec1544_37f2_7a28_8a2d_0195fea35441_TBX8671_11 , y = 11ec1544_37f2_7a27_8a2d_793050b2eda6_TBX8671_11 , so we can plug these values into the formula and solve for k:

11ec1544_37f2_7a27_8a2d_793050b2eda6_TBX8671_11 = k(11ec1544_37f2_7a28_8a2d_0195fea35441_TBX8671_11)
k = 11ec1544_37f2_7a27_8a2d_793050b2eda6_TBX8671_11 / 11ec1544_37f2_7a28_8a2d_0195fea35441_TBX8671_11
k = 5

Now we can use this value of k and the given value of x = 15 to find y:

y = kx
y = 5(15)
y = 75

Therefore, the answer is B) 60.

If Y Varies Directly with X , and If