Problema Solution
A student invested some money at 6% annual interest and twice as much money at 7% annual interest. After one year he earned $84 in interest. How much was invested at each rate.
Answer provided by our tutors
suppose he invested x in 6% so that he invested 2x in 7%
he earnd $84
that 84 = 0.06x+0.07*2x
so x = 420
that is he invested 420 in 6% invested 840 in 7%