Before she took her last exam, the average of Tara's exam scores was 89 she figures that if she scores 97 on the last exam, her average for all the exams will be 90. If she scores a 73 her average for all the exams will be 87. How many exams, including the last one are givin in the class?
2006-12-21 14:01:45 · 4 answers · asked by hockeygirl1101 1 in Entertainment & Music ➔ Jokes & Riddles
Not enough info to solve
2006-12-21 14:03:52 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Let n be the number of exams (including the last one) and let S be the sum of all of Tara's exam scores before the last exam.
Tara's average before the last exam is 89, so S/(n - 1) = 89, or S = 89(n - 1).
If she gets 97 on the last exam, the sum of all her scores will be S + 97 = 89(n - 1) + 97 = 89n - 89 + 97 = 89n + 8.
Her average will be (S + 97)/n = 90, so 90n = S + 97 = 89n + 8. This means that n = 8 (the number of all the exams, including the last one).
This answers the question, but let's look at the other information, too.
If she gets 73 on the last exam, the sum of all her scores will be S + 73 = 89(n - 1) + 73 = 89n - 89 + 73 = 89n - 16.
Her average will be (S + 73)/n = 87, so 87n = S + 73 = 89n - 16. So 2n = 16, or n = 8. This agrees with the first answer!
2006-12-21 22:48:57 · answer #2 · answered by wild_turkey_willie 5 · 0⤊ 0⤋
Thats too much thinking for a yahoo answers question.
2006-12-21 22:04:40 · answer #3 · answered by kknights81 1 · 0⤊ 0⤋
is this your hmwk?
2006-12-21 22:06:37 · answer #4 · answered by Dancer_for_life 4 · 0⤊ 0⤋