An integer is defined as upright if the sum of its first two digits equals its third digit. For example, 145 is an upright integer since 1+4=5. How many positive three-digit integers are upright?


Last week’s question and solution

Problem: Daniel is having dinner with a friend. He buys five dishes and his friend buys three dishes. At the last minute another friend comes to eat with them and pays $4 for his share of the meal. If all the dishes have the same value, how should the money be divided between Daniel and his first friend?

Solution: Since the second friend paid $4, the total cost of the meal must be $4 x 3 = $12. Eight dishes were eaten, so each one costs $1.50. Daniel brought 5 x $1.50 = $7.50 worth of food, and since his share was $4, he should receive $3.50. The first friend brought 3 x $1.50 = $4.50 worth of food and should receive 50 cents.


From Eric Lass, 7th & 8th grade Math Teacher


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