Suppose that a telephone company offers two long distance plans A and B. The monthly charges for A and B are $25 and $5 respectively. While the charges per minute for A is 5 cents per minute, while B is 12 cents per minute.
For how many minutes of long distance calls would plan B be financially advantageous?
If we let x be the duration of long-distance calls in minutes and if B is cheapter, then...
B<A5+5100x<25+5100xmodel, recall that $1=100cents12100x−5100x<25−5Subtract 5100x and 57x100<20Multiply both sides by 1007x<1007(20)x<20007
It shows that the duration of call is less than 20007min, Plan B will be cheapter than Plan A.
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