In this problem, $90=100$90=100, therefore we need to find 30%30% and subtract it from the original to get the discount price of 70%70% of the original. An easy way to find 30%30% is to find 10%10% by dividing the original amount by 100100, then multiplying by 33.
100%=$90100%=$90
As 100/10=1010010=10, we can divide by 100100 to find 10%10%
90/10=$99010=$9
Therefore 10%=910%=9
As we want to find 30%30%, we need to find out how many times 1010 goes into 3030
30/10=33010=3 Therefore we need to multiply the 10%10% we found by 33
$9 xx 3=$27$9×3=$27 This is therefore 30%30% of the original amount.
If you wanted the amount of the discount, the answer is color(red)($27)$27
But this isn't it, we found 30%30% but we want 70%70% of the original amount, so we minus the answer we have from the original:
$90-$27=$63$90−$27=$63
This is like saying
100%-30%=70%100%−30%=70% which is the value we want.
therefore discounted price=color(red)($63
If you wanted the price after discount the answer is $63