This problem became a GREAT DISCUSSION QUESTION with my 4th Grade Students!! Which method would you choose? 
 
Please check out my YouTube Channel "Math Challenge" for the SOLUTION! SCAN that QR Code to take you right to the video!
 
I would be SUPER DELIGHTED AND HAPPILY EMBARRASSED LOL if you showed my video to your class explaining the solution! 

I would LOVE to know how the problem worked out for your kiddos :) 
Any requests for future problems is greatly appreciated!
THANK YOU SO MUCH!! 

E-mail: knishimori@bridgemath.com