Question 1159607
Katherine leaves home for school, riding her bicycle at a rate of 12miles/hr.  Twenty minutes after she leaves, her mother sees Katherine's English paper on her bed and leaves to bring it to her.  If her mother drives at 36miles/hr, how far must she drive before she reaches Katherine?
<pre>Let distance she should drive, be D
With {{{matrix(1,3, TIME, "=", DISTANCE/SPEED)}}}, we get the following TIME equation: {{{matrix(2,3, D/12 - 20/60, "=", D/36,
D/12 - 1/3, "=", D/36)}}}
3D - 12 = D ------ Multiplying by LCD, 36
   - 12 = D - 3D
   - 12 = - 2D
Distance to be driven, or {{{highlight_green(matrix(1,6, D, "=", (- 12)/(- 2), "=", 6, miles))}}}