Question

After school, Marcus can walk 1 mile to the library in about the same time he can bike 2.5 miles to the sporting goods store. His speed on the  bike is 6 mi/h faster than his walking speed. what is Marcus' walking speed?

Answer 1

$d-distance\\t-time\\v-speed$

$d_1=1mile\\d_2=2.5miles\\t_1=t_2\\v_1+6=v_2\\\\v=\frac{d}{t}\to vt=d\to t=\frac{d}{v}\\\\\frac{d_1}{v_1}=\frac{d_2}{v_2}\\\\\frac{1}{v_1}=\frac{2.5}{v_1+6}\\\\cross\ multiply:\\2.5v_1=v_1+6\\2.5v_1-v_1=6\\1.5v_1=6\ \ \ \ \ /:1.5\\v_1=4\\\\Answer:Marcus'\ walking\ speed\ is\ 4\ mph.$