Question 1049571
Pratap Puri rowed 14 miles down a river in 2 ​hours, but the return trip took him 3 1/2 one half  hours. Find the rate Pratap can row in still water and find the rate of the current
<pre>Average speed down-river: {{{matrix(1,4, 14/2, or, 7, mph)}}}
Let speed in still water be S, and rate of current, C
Down-river equation: S + C = 7 ------- eq (i)

Average speed up-river: {{{matrix(1,8, 14/(3&1/2), "=", 14/(7/2), "=", 14 * (2/7), "=", 4, mph)}}}
Up-river equation: S - C = 4 ------- eq (ii)
2S = 11 -------- Adding eqs (ii) & (i)
S, or rate in still water = {{{11/2}}}, or {{{highlight_green(highlight(matrix(1,2, 5.5, mph)))}}}

5.5 + C = 7 ------- Substituting 5.5 for S in eq (i)
C, or rate of current = 7 - 5.5, or {{{highlight_green(highlight(matrix(1,2,1.5, mph)))}}}