Question

A swimmer finished a total of 6,400 meters in races before his last race. He competed in twelve 400-meter races. The rest of his races were 200- meter races. How many of his races were 200-meter races?

Answer 1

The total distance swimmer finished is 6400 meters. The distance travlled in 400 meter races and 200 meter races is equal to total diatance. So equation for x number of 200 meter races is,

$\begin{gathered} 12\cdot400+x\cdot200=6400 \\ 200x=6400-4800 \\ x=\frac{1600}{200} \\ =8 \end{gathered}$

So there are 8 number of 200 meter races.