SOLUTION: Jim and members of his Spanish club are going to Costa Rica over spring break. Before his trip, he purchases 10 travelers checks in denominations of $20, $50, and $100, totaling $3

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Jim and members of his Spanish club are going to Costa Rica over spring break. Before his trip, he purchases 10 travelers checks in denominations of $20, $50, and $100, totaling $3      Log On


   



Question 841466: Jim and members of his Spanish club are going to Costa Rica over spring break. Before his trip, he purchases 10 travelers checks in denominations of $20, $50, and $100, totaling $370. He has twice as many $20 checks as $50 checks. How many of each type of denomination does he have?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = number of $20 checks
Let +b+ = number of $50 checks
Let +c+ = number of $100 checks
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(1) +a+%2B+b+%2B+c+=+10+
(2) +20a+%2B+50b+%2B+100c+=+370+
(3) +a+=+2b+
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there are 3 equations and 3 unknowns,
so it's solvable
Multiply both sides of (1) by +100+
and subtract (2) from (1)
(1) +100a+%2B+100b+%2B+100c+=+1000+
(2) +-20a+-+50b+-+100c+=+-370+
+80a+%2B+50b+=+630+
Substitute (3) into this result
+80%2A2b+%2B+50b+=+630+
+210b+=+630+
+b+=+3+
and, since
(3) +a+=+2b+
(3) +a+=+6+
and
(1) +a+%2B+b+%2B+c+=+10+
(1) +6+%2B+3+%2B+c+=+10+
(1) +c+=+1+
There are 6 $20 checks
There are 3 $50 checks
There is 1 $100 check
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check:
(2) +20a+%2B+50b+%2B+100c+=+370+
(2) +2a+%2B+5b+%2B+10c+=+37+
(2) +2%2A6+%2B+5%2A3+%2B+10%2A1+=+37+
(2) +12+%2B+15+%2B+10+=+37+
(2) +37+=+37+
OK