A shopkeeper buys $240$ pears for $60$ dollars . Some of these pears are bad and they are thrown away. The remaining pears are sold at $35$ cents each , thus making a profit of $19.80$ dollars . Calculate the percentage of pears that are thrown away.
My workings -
Let $x$ be the number of pears thrown away
Selling price of remaining pears = $(240-X)(0.35) = (84 - 0.35x) $
Profit = selling price of the remaining pears - cost price
$19.80 = ( 84 - 0.35x)$ - cost price
I'm not sure what to put into the 'cost price of remaining pears' section for the remaining to find the value of 'X'
The remaining pears are worth $35$ cents each. The profit from them was $79.80$ dollars (because we can add the $60$ dollars he paid. We can divide:
$$\frac{7980}{35} = 228$$
So they kept $228$ pears, and $240 - 228 = 12$ pears that were thrown away.
$12$ is $\frac{1}{20}$ of $240$, or $5$%.
So $\boxed{5\text{%}}$ of the pears were thrown away.