Question 520641
A boy cycles from his house to a friend's house at 20km per hour and home again at 25km per hour.
 If his round trip takes 9/10 of an hour, how far is it to his friend's house?
:
Let d = the one-way distance to friends house
;
Write a time equation, time = dist/speed
{{{d/20}}} + {{{d/25}}} = .9
Multiply by 100 to clear the denominators, solve for d