Brain Busters (Caisse-cerveau)

Brain Buster challenges are designed to encourage the development of problem-solving strategies.  These are part of our classroom economy.  Each month, three new Brain Busters will be added to this page.  A successful completion of a Brain Buster challenge will be paid $50 and an unsuccessful full attempt will be paid $25.  Brain Busters Solver sheets can be found in the classroom mailboxes.


9 Arrange the numbers from 1 to 25 in a 5×5 grid so that each row, column, and diagonal adds up to the same number.
8 A number of children are standing in a circle. They are evenly spaced and the 7th child is directly opposite the 18th child. How many children are there altogether?
7 Elizabeth headed to the mall with $60. If she spends 1/4 of her money on clothes, $30 on CD’s, and 10% of her original money pigging out at the food court, how much cash will she have left?


6 What’s the mystery number?

  • It’s greater than one million but less than ten million.
  • It’s an even number.
  • None of the digits is less than 3.
  • No digit is used more than once.
  • The sum of the digits in the ones period is 12.
  • The digit in the ten thousands place is equal to the sum of the digits in the tens and hundreds places.
  • The digit in the millions place is 2 more than the digit in the thousands place.
  • The digit in the hundred thousands place is twice the digit in the tens place.
5 Fiona and her friends went shopping for fresh produce. They spent $1.20 for a bag of squash, which sold for $0.60 per pound. Their bag of 6 equally-sized apples weighed the same as their bag of 2 identical squash. Their 8 peaches, all about the same size, weighed as much as 3 apples and 1 squash. They also purchased a small pumpkin that weighed the same as 12 peaches. How much did the pumpkin weigh?
4 Federico starts saving lira on Sunday. He starts with one hundred lira in the collection, and each day (including Sunday) his papa agrees to double the number of lira in his collection. Federico also adds ten lira to the collection each day. How many lira does Federico have in his collection at the end of the day on the following Saturday (7 days later)?


3 It was Jonathan’s first day at his new school along with six other new students who were starting the spring session. The teacher suggested that it would be a good idea for each of the new students to get to know each other better. The teacher said, « I’d like each of you to have lunch with each of the other new students. » Since there were 7 new children in the class, how many total lunches would it take for them to have lunch with each of the new students only once?
2 Massimo and Lucia work at the same pace, and together they can paint an entire house in 9 days. They recruit Antonio, who works at the same pace as they do, to help them paint the house.  How long will it take the three of them to paint the entire house?
1 If I buy an apple and a banana, the cost will be $1.19. If I buy an apple and a pear, the cost will be $1.45. If I buy a banana and a pear, the cost will be $1.40. What are the individual prices?

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