Mental Blocks Math Brainteaser (Pre-Algebra Level)

[Otis]

To build a tower the same height as a large block, I can stack 28 medium blocks, or 76 small blocks. To build a tower the same height as 8 large blocks stacked, I can use 161 medium blocks plus how many small blocks?



[imath]\;[/imath]

 

[lookagain]

This is a worked out solution:

Spoiler

28 med. blocks correspond to 76 small blocks,
so 7 med. blocks correspond to 19 blocks.

161 divided by 28 equals 5 with remainder 21.

Then 161 med. blocks correspond to 5 large blocks with 21 med. blocks
left over. If you could add 7 more med. blocks to the remaining 21, you
would have 28 medium blocks to make an additional sixth large block.
To add the corresponding amount, you instead add 19 small blocks.

Finally, to reach a total of 8 large blocks, you need to add 2 more large blocks.
That means adding 2*76 small blocks = 152 small blocks.

Therefore, the total number of small blocks to be added is 19 + 152 = 171.