Every Day Counts!

Today in Math Workshop, these three students shared some awesome math strategies for finding sums using "mental math" while we worked on our Daily Depositor in Every Day Counts.

Student 1 had an easy way to add 29 + 30 + 31. He used compensation to take one away from 31 (30) and add 1 to 29 (30) so that he created a new problem that could easily be solved mentally: "30 + 30 + 30". 29 + 30 + 31 = 90!

Student 2 also used compensation to solve 253 + 90. Here are the steps he used to find the sum:

253 + 100 = 353

353 - 10 = 343.

He knew that by adding 100 and subtracting 10 to 253, that he was adding a net of +90.

253 + 90 = 343

Student 3 used another creative method, decomposition, to solve the same problem: 253 + 90

He decomposed 253 into 250 + 3.

He decomposed 90 into 50 + 40.

His new problem became: 250 + 3 + 50 + 40.

He first combined 250 + 50 to get 300. He then added 40 and 3 to 300 to get his final answer:

300 + 40 + 3 = 343

Wow! These math strategies are spectacular, and it's only the 8th day of 4th grade. Mr. Pinchot and I are so excited to see the other strategies our kids have in their tool belts for solving math problems using number sense and efficiency!