Lower Elementary:
Question: Walter is buying books from a library. He bought 4 books: 3 that were $1.98 each and 1 that was $3.01. What is the total cost of the 4 books?
Answer: $8.95
Solution: First, find the total of the 3 books. Since $1.98 is 2 cents less than $2, we can count 2, 3 times and then subtract 2 cents, 3 times. 1.98 + 1.98 + 1.98 = 2 + 2 + 2 – .02 – .02 – .02 = 6 – .06 = 5.94. Add the price of the 4th book to get the total. $5.94 + $3.01 = $8.95
Upper Elementary:
Question: Phoebe and her parents are eating a pie. Her dad eats a quarter of the pie. Her mom eats a third of what is left. Phoebe ate half of the pie that was left after her mom ate her portion. How much of the pie is left?
Answer: 1/4 of the pie
Solution: Phoebe’s dad eats a quarter of the pie, so there is 3/4 left. Her mom ate a third of the 3 quarters that was left. Break 3/4 into 3 equal parts: 1/4 + 1/4 + 1/4. A third of 3/4 is 1/4. So the mom ate 1/4 of the pie. Now there is 2/4 = 1/2 of the pie left after the mom ate her portion. Phoebe ate half of what was left after her mom ate her portion. Half of 1/2 is 1/4. There is 1/4 of the pie left.
Middle School:
Question: In a survey of 1,000 people, 10% said they do not watch TV, 25% said they watch 1-3 hours of TV a day, 40% said they watch 3-5 hours of TV a day, and the rest said they watch more than 5 hours of TV a day. How many people said that they watch more than 5 hours of TV a day?
Answer: 250 people
Solution: First we need to find the percent of people who watch more than 5 hours of TV. To find the percent of people who watch more than 5 hours, take the total of all the other percents and subtract it from 100%. 10 + 25 + 40 = 75. 100–75 = 25. The percent of people who watch more than 5 hours of TV a day is 25%. Now, we need to find 25% of 1,000. Percent means for every hundred. There are 10 hundreds in 1,000. So we take 25, 10 times. 250 people watch more than 5 hours of TV a day.
Algebra and Up:
Question: In a standard deck of cards, what is the probability of drawing a spade, keeping it, and then drawing a red card?
Answer: 13/102
Solution: There are a total of 52 cards in a deck. Each suit has 13 cards. So there are 13 spades in the deck. The probability of drawing a spade as the first card is 13/52 = 1/4. Now there are 51 cards left in the deck. There are 26 red cards, so there is a 26/51 probability of drawing a red card after drawing one card. Multiply the two probabilities together to get the total probability. 1/4 x 26/51 = 1/2 x 13/51 = 13/102. The probability of drawing a spade and then a red card is 13/102.
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