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Question 1019910: Larry has 4-cent stamps and 9-cent stamps, which he can combine to produce various amounts of postage. For example, he can make 40 cents by using four 9-cent stamps and a 4-cent stamp, or by using ten 4-cent stamps. However, there are some amounts of postage he can't make exactly, such as 10 cents. What is the largest number of cents that Larry cannot make exactly from a combination of 4- and/or 9-cent stamps?Explain how you know your answer is correct. (You should explain two things: why Larry can't make the amount of your answer, and why he can make any bigger amount.)
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Larry has 4-cent stamps and 9-cent stamps, which he can combine to produce various amounts of postage. For example, he can make 40 cents by using four 9-cent stamps and a 4-cent stamp, or by using ten 4-cent stamps. However, there are some amounts of postage he can't make exactly, such as 10 cents. What is the largest number of cents that Larry cannot make exactly from a combination of 4- and/or 9-cent stamps?Explain how you know your answer is correct. (You should explain two things: why Larry can't make the amount of your answer, and why he can make any bigger amount.)
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What you should do::
List the multiples of 4 from 4 to 4*10 = 40
List the multiples of 9 from 9 to to 4*9 = 36
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If you have to, list the sums you can make by
taking a number from each of the lists.
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Put the sums in rank-order(smallest to largest)
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Answer the questions.
Cheers,
Stan H.
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