Math Adventures/Double check

Solve each of the following math problems. If you quickly gave an intuitive answer, carefully recheck the math. Write out an equation and use a calculator if necessary to double check your answers.

  1. If 8 men can dig 8 holes in 8 days, how many similar holes can 4 men dig in 4 days?
  2. A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?
  3. A shopkeeper buys an item for $60, sells it for $70, then buys it back for $80, and sells it again for $90. How much profit did he make?
  4. A boat goes 30 km downstream in 3 hours and returns upstream in 5 hours. What’s the speed of the current?
  5. A family has two children. One is a boy. What is the probability both are boys?
  6. You flip a coin until you get heads. What is the expected number of flips?
  7. A 10 ft ladder leans against a wall. The bottom slides 3 ft away. How far down does the top slide?
  8. What is the maximum number of pieces you can get from a cake with 3 straight cuts?
  9. Four people must cross a bridge at night with one flashlight. Each person walks at a different speed. Only two can cross at a time, and the flashlight must be carried back and forth. What’s the minimum total time?

Answers

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