M is directly proportional to r cubed. When r=4, M=160. A) Work out the value of M when r=2.
B) Work out the value of r when M=540.

A. M= 20

B. r = 6

Step-by-step explanation:

M=kr³

where k is the constant

M= 160 , r 4

160= k(4)³

k = 160/4³= 2.5

A. when r= 2 , M= kr³

M= 2.5(2)³ = 20

B. when M= 540, find r

M= kr³

r³ = M/k

r³ = 540/2.5

r³= 216

r = 6

1st digit - 0-9 = 10 numbers

2nd digit = 9 numbers

3rd digit = 8 numbers

4th digit = 7 numbers

5th digit = 6 numbers

10 * 9 * 8 * 7 * 6 = 30,240 zip codes