Open Middle®
Directions: Using the digits 1 to 9, at most one time each, place a digit in each box so that the difference is as close to 50 as possible. NOTE: The digits used in the difference can be repeated.
Hint
What digit could go in the tens place to be close to 50?
Answer
53.1 – 2.9 = 50.2
52.9 – 3.1 = 49.8
52.9 – 3.1 = 49.8
Source: Giselle Garica
If the answer is correct then there are too many boxes in the second number for the setup of the problem. What you are suggesting is that it is a 2 digit number with a decimal subtracted by another 2 digit number with a decimal. If you want to fix that the “setup” it should look like this ..
[][].[] – [].[] = ?
Otherwise, the answer key is wrong and should be something like this:
75.1 – 24.9 = 50.2
OR
73.9 – 24.1 = 49.8
thxs for real info
I told my students they could use 0-9 and then the second number being 3 digits was was ok. Here’s what they came up with:
73.9 – 24.0 = 49.9
74.0 – 23.9 = 50.1
My students argued that the directions didn’t specify that digits had to be positive and were able to make exactly 50 with a couple of different combinations:)
35.2-(-14.8)
34.2-(-15.8)
32.4-(-17.6)
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I use your boxes to get 81.2 – 30.9 = 50.3
90.5-40.6=49.9
One of my 5th grade students said, “69.4 – 19.5” to get 49.9.
The 9 has been repeated. Try 69.2 – 18.7 = 50.5 or 68.2 – 17.9 = 50.3