Total purchase = (unit cost)(# of pounds purchased)
Here, that total is ($0.98/lb)(3.5 lb) = $3.43 (answer)
Okay. So, she buoyant 5.65 lbs of roast beef for $4.50. Multiply both of those numbers to get 25.425 or 25.43 when rounded to the nearest hundredth. So the total cost was $25.43. However, we now have to divide the amount by 6.5. 25.43/6.5 is 3.912 and other odd numbers or 3.91 when rounded to the nearest hundredth. The cost per sandwich was $3.91.
To reverse a percentage decrease you divide it by the decrease (+ 100%)
For example we will pick the number, 100, which is decreased by 15% to 85.
To make 85 back to 100 we divide it by the decrease (1-0.15):
85 / 0.85 = 100
To find out how much 85 increased to get back to 100, we do:
15 / 85 = 0.1765 = %17.65
15 is the reduction/difference, and 85 is the with reduction total.
Because percentages stay the same, this is applicable to any numbers, from this, we know that whenever something is reduced by 15% - when restored to it's original is increased by %17.65
The answer is %17.65