Ivy, Ken, and Ron shared some sweets in the ratio 5: 4 : 2. Ken gave some of his sweets to Ivy and Ron. As a result, his sweets decreased by 75%. After receiving some sweets from Ken, Ron's. Find the sweets increased by 50%. Find the percentage increase in the number of sweets that Ivy had.
+486 ivy$=5k$ for some part k
ken$=4k$ for some part k
ron$=2k$ for some part k
$4k-c=0.75(4k)=3k$
$2k+c=1.5(2k)=3k$
$4k-c=3k$
$2k+c=3k$
Setting these equal, ignoring the 3k, we see $4k-c=2k+c$, so:
$4k-c=2k+c$
$2k=2c$
$k=c$.
So Ivy's sweets increased by $k$, so her percentage increase was $\frac{6}{5}=120=\boxed{20}$ percent increase
