SOLUTION: Ali,Ben and charles shared teh cost of a present. The ratio of the amount paid by ali to the total amount paid of Ben adn charles was 2: 3 while Ben's share was 20% o fthe total am

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Question 894900: Ali,Ben and charles shared teh cost of a present. The ratio of the amount paid by ali to the total amount paid of Ben adn charles was 2: 3 while Ben's share was 20% o fthe total amount paid by ali and charles. Given that charles paid 84 more then Ben, How much did the present cost.?
Found 2 solutions by richwmiller, josmiceli:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
a+b+c=p
2/3=a/(b+c),
b=.2*(a+c),
c=b+84
a = 126, b = 52.5, c = 136.5, p = 315
The present cost 315


Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let the amounts paid by each = a, b, and c
given:
(1) +a+%2F+%28+b+%2B+c+%29+=+2%2F3+
(2) +b+=+.2%2A%28+a+%2B+c+%29+
(3) +c+=+b+%2B+84+
------------------------
This is 3 equations and 3 unknowns, so it's solvable
Multiply both sides of (1) by +3%2A%28+b+%2B+c+%29+
(1) +3a+=+2%2A%28+b+%2B+c+%29+
(1) +3a+=+2b+%2B+2c+
and
(2) +b+=+.2a+%2B+.2c+
(2) +.2a+=+b+-+.2c+
(2) +a+=+5b+-+c+
--------------------
Substitute (2) into (1)
(1) +3%2A%28+5b+-+c+%29+=+2b+%2B+2c+
(1) +15b+-+3c+=+2b+%2B+2c+
(1) +13b+=+5c+
(1) +b+=+%28+5%2F13+%29%2Ac+
----------------------
Substitute (1) into (3)
(3) +c+=+b+%2B+84+
(3) +c+=+%285%2F13%29%2Ac+%2B+84+
(3) +13c+=+5c+%2B+1092+
(3) +8c+=+1092+
(3) +c+=+136.5+
and
(3) +c+=+b+%2B+84+
(3) +b+=+c+-+84+
(3) +b+=+136.5+-+84+
(3) +b+=+52.5+
and
(1) +a+%2F+%28+b+%2B+c+%29+=+2%2F3+
(1) +a+%2F+%28+52.5+%2B+136.5+%29+=+2%2F3+
(1) +a+%2F+189+=+2%2F3+
(1) +3a+=+378+
(1) +a+=+126+
and
+a+%2B+b+%2B+c+=+126+%2B+52.5+%2B+136.5+
+a+%2B+b+%2B+c+=+315+
The present costs $315
------------------------
check:
(2) +b+=+.2%2A%28+a+%2B+c+%29+
(2) +b+=+.2%2A%28+126+%2B+136.5+%29+
(2) +b+=+.2%2A262.5+
(2) +b+=+52.5+
OK
Hope I got it!