Open Middle®
Directions: Use the digits 1-9, at most once, to complete the equation.
What is the greatest result you can make?
What is the least result you can make?
Hint
What numbers work (or won’t work) for the tens digits?
Could the result have a zero in the one’s place?
Could the least result be less than 10?
Could the greatest result be greater than 100?
Could the result have a zero in the one’s place?
Could the least result be less than 10?
Could the greatest result be greater than 100?
Answer
There are many answers. Here are some:
27 – 8 = 14 + 5
25 – 8 = 13 + 4 (or 14 + 3) ~ least result of 17 = 17
95 – 2 = 87 + 6 (or 86 + 7) ~ greatest result of 93 = 93
Source: Molly Rawding
High: 89
Low: 17
This question is NOT for grade one. They are not required to add past 18 or subtract any higher than 18.
Sh, but doesn’t 1.NBT.4 state that students should be adding within 100 and 1.NBT.6 subtract units of 10 from a 2-digit number? Shouldn’t our students be exposed to rigor and creative/critical thinking?