3. John ate half of the M&Ms in the package. Later, his sister ate 1/3 of the remaining M&M’s. How many M&M’s are left?
This one is just like the plants problem. It is also shows by far the most common error that students make when trying to write subtraction problems. Our natural inclination is to make the second fraction a fraction of the first fraction, but that makes the answer a half minus a third of a half: 1/2 - (1/3)x(1/2), rather than 1/2 - 1/3
To make this a plain subtraction problem, you need to fix the second fraction:
| 1/2 - (1/3)x(1/2) | Original: John ate half of the M&Ms in the package. Later, his sister ate 1/3 of the remaining M&M’s. How many M&M’s are left? |
| 1/2 - 1/3 | Fixed: John ate half of the M&Ms in the package. Later, his sister ate 1/3 of the package of M&M’s. How many M&M’s are left? |