direct proportion please helpWatch
a is directly proportional to the cube of b
When a=20, b=2
Find a when b=4
For my answer I got 160, is that correct?
I didn't guess, I was substituting numbers in. I thought it would be (D) because 18/3 = 6 and y=6. But I just realised that (A) also equals 6 however (D) is in the equation form for inverse, so I'm not sure if it's correct I just assumed it's my only other option.
Then substitute the numbers into That to get the value for k instead of working backwards from the multiple choice answers.