Can You Do Fourth Grade Math?
Posted Mar 24th, 2006 at 10:45 pm in Life in General
My wife (the student teacher) told me of an absurb question that appeared in a fourth grade class on review material for the state assessment test. Can anyone spot the problems and provide a right answer? There is a set of numbers that gives a mathematically valid solution.
Bella’s age minus her brother’s age is 12. Bella’s brother is 4 times older than Bella. What are the ages of Bella and her brother?
When they said they were making the standards tests harder, I guess they weren’t kidding.
What state is this again? Texas?
I didn’t get it, but it can be expressed algebraically as:
x -b = 12b = 4x
*whoosh* Not a clue.
By my calculations, Bella will be born in 2010, and her brother will be born in 2022. Now that’s what I call family planning.
If they start giving out negative years, I’d like to apply for a few, please.
Wait, the answers are negative numbers? I don’t think I learned negative numbers until about 6th or 7th grade.
Yes, everybody got the answer right. Dante set the problem up right in the first comment.
To solve, take the first equation and solve for x.
x – b = 12.
Thus, x = 12 + b.
Now, plug this value in for x in the second equation.
b = 4(12 + b)
b = 48 + 4b
-48 = 3b
b = -16
Bella’s brother is -16 years old.
Now take b and plug it back into either equation and solve for x to get Bella’s age.
-16 = 4x
x = -4
So Bella is -4 years old.