Vitamin A and E

[apoorva_srivastva]

One gram of a certain health food contains 7 percent of the minimum daily requirement of vitamin E and 3 percent of the minimum daily requirement of vitamin A. If vitamins E and A are to be obtained from no other source, approximately how many grams of the health food must be eaten daily to provide at least the minimum daily requirement of both vitamins?

A. 3
B. 7
C. 10
D. 14
E. 33

I just could not comprehend the question!!!

[parker.mitchell]

A good way to approach this one is to say, "Ok, I need 100 grams of Vit. A, and 100 of Vit. E. How much of this stuff do I need to eat to get there?" Since one gram of the stuff contains 7 grams of E (7% of 100) and 3 grams of A (3% of 100), we know that we only need to focus on Vitamin A, because once we get our necessary amount if it, we'll also have Vitamin E covered (doesn't work the other way). So, we just need to focus on getting 100 grams of vitamin A. If one serving gives us 3 grams, how many servings do you need to get to 100?

[apoorva_srivastva]

A good way to approach this one is to say, "Ok, I need 100 grams of Vit. A, and 100 of Vit. E. How much of this stuff do I need to eat to get there?" Since one gram of the stuff contains 7 grams of E (7% of 100) and 3 grams of A (3% of 100), we know that we only need to focus on Vitamin A, because once we get our necessary amount if it, we'll also have Vitamin E covered (doesn't work the other way). So, we just need to focus on getting 100 grams of vitamin A. If one serving gives us 3 grams, how many servings do you need to get to 100?

But when we consider Vita A how do we cover Vit E as well...it may be very trvial but I am confused!!!


We consider Vitamin A just because it is in lower concentration...Am i right on this one

regards,
apoorva

[RonPurewal]

We consider Vitamin A just because it is in lower concentration...Am i right on this one

regards,
apoorva

correct. so basically you just divide 100 by 3, arriving at 33 1/3, so (e) is the correct answer.

the point of this problem is more what NOT to do. i.e., you don't concentrate at all on the ingredient that you're getting more of, and you definitely don't add the 3 and 7 percent figures together.

by the way, the word "approximately" is a giveaway that you're NOT going to get an exact number. i have NEVER seen a problem whose problem statement said "approximately" but whose answer wound up in exact form.
this observation should cast additional doubt on some wrong answers.
for instance, (c) is what you get if you add the 7 and 3, and then divide 100 by that figure. the problem (aside from the fact that it's incorrect, of course) is that you get exactly 10 from that; since the problem says "approximately", you should be suspicious.

--

if you still don't understand, try an analogy.

let's say that granola bars come in bulk packs of 7 chocolate chip and 3 oatmeal raisin, and that you can't buy the flavors separately.

you need 100 chocolate chip and 100 oatmeal raisin bars for a catering event.

how many bulk packs do you have to buy?

same deal - you have to buy enough bulk packs to get 100 of BOTH kinds, which means you have to buy 33 1/3 of them (i.e., buy 34 of them) to get enough of the oatmeal raisin kind.
true, you'll have a whole lot of chocolate chip bars just sitting around, but that is irrelevant.