The answer is B. 120
nCr = n! / ((r! * (n - r)!)
n = 10
r = 3
10C3 = 10! / ((3! * (10 - 3)!)
= 10! / ((3! * 7!)
= (10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1) / (3 * 2 * 1 * 7 * 6 * 5 * 4 * 3 * 2 * 1)
= 3628800 / 30240
= 120
Well the square root of 72 is 8.485 and the square root of 45 is 6.708. hope this helps :)
2*10 =20
4*5 =20
8 *5/2 = 20
answer is B inverse variation, xy = 20