15
One half billion divided by 16 is 31,250.
15
0.0438
0.032
31,250
15
15 ÷ 16 ÷ 3 = 0.3125
2.3333
0.0068
Well, 4 divided by 16 is 1/4, so 16 into 400 billion it must be 100 billion times that. That makes it 25 billion. Or if you like, 400 divided by 16 is 25, leading to the same answer.
62500000000