math
posted by deepa on .
roated beef has 20g of protein and 11g of calcium per serving. serving of mashed potatoes has 2g of protein and 25g of calcium, how many servings of each are needed to supply 29 grams of protein and 61 grams of calcium?

Let the number of servings of beef be B, and let the number of servings of mash be M. Then we know that:
20B + 2M = 29
11B + 25M = 61
Multiply the first equation by 25, and the second one by 2 to get:
500B + 50M = 725
22B + 50M = 122
Subtract the second equation from the first one to get:
478B = 603
So B = 603/478 = 1.261, and M = (6111B)/25 = 1.885
Check it:
(20 x 1.261) + (2 x 1.885) = 29
(11 x 1.261) + (25 x 1.885) = 61
So you need 1.261 portions of beef and 1.885 portions of mash.