Question 1123893

Ahmad brought a number of shares for Rs 1875.he reserved 15 of theme and sold remaining for Rs1740 making a profit of 4 per share on the cost price.how many share did he buy.
<pre>Let number of shares be S
Then cost of each share = {{{"1,875"/S}}}
Reserving 15 shares means that he had S – 15 remaining
Therefore, he sold each share for {{{"1,740"/(S - 15)}}}
We then get: {{{matrix(1,3, "1,875"/S, "=", "1,740"/(S - 15) - 4)}}}
1,875(S – 15) = 1,740S – 4S(S – 15) ------ Multiplying by LCD, S(S – 15)
{{{matrix(1,3, 1875S - 15("1,875"), "=", 1740S - 4S^2 + 60S)}}}
{{{matrix(1,3, 4S^2 - 1800S + 1875S - 15("1,875"), "=", 0)}}}
{{{matrix(1,3, 4S^2 + 75S - "28,125", "=", 0)}}}
{{{matrix(1,3, 4S^2 + 375S - 300S - "28,125", "=", 0)}}}
S(4S + 375) – 75(4S + 375) = 0
(S – 75)(4S + 375) = 0
S, or number of shares he purchased = {{{highlight_green(75)}}}	      OR        S = {{{- 375/4}}} (ignore)