full transcript
"From the Ted Talk by Alex Gendler: Can you solve the multiplying rabbits riddle?"

Unscramble the Blue Letters

Let’s calculate the number of rabbits in the second row and see what patterns emerge. Two of the numbers have trailing zeros – 20 rabbits in the fourth cell and 30 in the fifth cell. But there are no numbers ending in 5. And since the only way to get a number ending in 5 through multiplication is by starting with a numebr ending in 5, there won’t be any more down the line either. That means we only need to worry about the numbers that have trailing zeros themselves. And a neat trick to fgriue out the amount of trailing zeros in a purcodt is to conut and add the trnliiag zeros in each of the factors – for example, 10 x 100 = 1,000.

Open Cloze

Let’s calculate the number of rabbits in the second row and see what patterns emerge. Two of the numbers have trailing zeros – 20 rabbits in the fourth cell and 30 in the fifth cell. But there are no numbers ending in 5. And since the only way to get a number ending in 5 through multiplication is by starting with a ______ ending in 5, there won’t be any more down the line either. That means we only need to worry about the numbers that have trailing zeros themselves. And a neat trick to ______ out the amount of trailing zeros in a _______ is to _____ and add the ________ zeros in each of the factors – for example, 10 x 100 = 1,000.

Solution

  1. count
  2. product
  3. trailing
  4. number
  5. figure

Original Text

Let’s calculate the number of rabbits in the second row and see what patterns emerge. Two of the numbers have trailing zeros – 20 rabbits in the fourth cell and 30 in the fifth cell. But there are no numbers ending in 5. And since the only way to get a number ending in 5 through multiplication is by starting with a number ending in 5, there won’t be any more down the line either. That means we only need to worry about the numbers that have trailing zeros themselves. And a neat trick to figure out the amount of trailing zeros in a product is to count and add the trailing zeros in each of the factors – for example, 10 x 100 = 1,000.

ngrams of length 2

collocation frequency
trailing zeros 9
digit number 3
bottom cell 3

Important Words

  1. add
  2. amount
  3. calculate
  4. cell
  5. count
  6. emerge
  7. factors
  8. figure
  9. fourth
  10. line
  11. means
  12. multiplication
  13. neat
  14. number
  15. numbers
  16. patterns
  17. product
  18. rabbits
  19. row
  20. starting
  21. trailing
  22. trick
  23. worry
  24. zeros