Maya’s mother asked her to buy some stamps. The available stamps were 3 cents, 9 cents, 11 cents, 17 cents and 21 cents. Her mother asked her to buy eight each of three stamps and nine of each of the remaining two stamps. Unfortunately, Maya forgot which stamps she was supposed to buy eight and nine of. Luckily, her mother had given her $5, the exact amount required to buy the stamps. Which stamps did she buy?
Quite a good one—it looks like trial and error but there’s a method. Start with the highest or lowest—the highest is (21+17)*9 + (3+9+11)*8 and the lowest is, of course, (3+9)*9 + (11+17+21)*8. Only if the highest is too high or the lowest is too low do you have to check further—and how high or low the two values are should give you an idea of what combination to try next. Thanks!
1 Comment on "Maya’s Stamps Errand"
Ramon says
December 23, 2022 @ 08:47
Quite a good one—it looks like trial and error but there’s a method. Start with the highest or lowest—the highest is (21+17)*9 + (3+9+11)*8 and the lowest is, of course, (3+9)*9 + (11+17+21)*8. Only if the highest is too high or the lowest is too low do you have to check further—and how high or low the two values are should give you an idea of what combination to try next. Thanks!
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