college Algebra
posted by meme on .
If y varies directly as x^2 and y=20 when x=4, find y when x=7?

Y = kx^2 = 20. x = 4.
k*4^2 = 20.
16k = 20. k = 20/16 = 5/4.
Y = kx^2.
Y = (5/4)*7^2 = 61 1/4 = 61.25. 
An investment of $63,000 was made by a business club. The investment was split into three parts and lasted one year. The first part of the investment earned 8% interest, the second 6% and the third 9%. Total interest from the investments was $4950. The interest from the investment was 4 times the interest from the second. Find totals of the three parts of the investment. What is the amount of the first part of the investment?

A hardware supplier manufactures three kinds of clamps, type A, B, and C. Production restrictions force it to make 20 more type C clamps than the total of the other types and twice as many as B clamps as type A clamps. The shop must produce 380 clamps per day. How many of each type are made per day? How many type A clamps are produced?