DAT math destroyer wrong solution?

[chackoaltes]

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First time posting, so I'm sorry if this is in the wrong place.
I'm looking at math destroyer practice test 2, problem 8:
Donna says that she was 21 when her daughter Trish was born. When asked how old her daughter is today, Donna said that in 6 years she will be 6 more than twice her daughter's age. How old is Trish?

Seems extremely simple. When I do the math, I get 21. Why on Earth are they saying the answer is 9? That doesn't even make sense. If her daughter is 9, then in 6 years, Donna will be 24 (6 more than 9*2). Which means Donna is currently 18 and her daughter isn't even born yet? Am I just missing something obvious?? Really scares me that I am using this resource to study, unless I'm embarrassingly wrong of course.

 

[artist2022]

The answer should be 9.***

Doing the math out, you get two equations: REDONE***
D = 21 + T
D + 6 = 2(T + 6) + 6 ----> D = 2T + 12 -- red is because the daughter will age too
Substitute and you get: 2T + 12 = 21 + T ---> T = 9.

 

[chackoaltes]

The answer should be 21, you're right. Both the DAT Destroyer and the Math Destroyer have a few mistakes in them, and this is one.

Doing the math out, you get two equations:
D = 21 + T
D + 6 = 2T + 6 ----> D = 2T
Substitute and you get: 2T = 21 + T ---> T = 21.

Your reasoning for the 9 is correct too, it doesn't make any sense lol. Don't worry, you got it right and the problem just has a typo. Keep going, you got this!

Thanks for the quick reply! Did you use the math destroyer to study? I was just wondering if you know of a comprehensive list of mistakes in their solutions or something like that? I don't want to learn the wrong thing if they published mistakes for a more difficult problem that I don't know how to do.

 

[BullGator1004]

Donna was 21 when her daughter was born. If Donna's daughter is 9 years old, that means Donna is 30. In 6 years Donna will be 36 and her daughter will be 15. 36 is 6 more than 15x2=30.

 

[artist2022]

Thanks for the quick reply! Did you use the math destroyer to study? I was just wondering if you know of a comprehensive list of mistakes in their solutions or something like that? I don't want to learn the wrong thing if they published mistakes for a more difficult problem that I don't know how to do.

Sorry, the answer is 9, thanks to BullGator1004! We can't forget to account for the fact that the daughter will age too lol! I did use the Math Destroyer, I did 16 of the 18 tests I think. I don't think there is a comprehensive list of mistakes unfortunately, sorry. This was just a tricky question, with a really easy mistake to make. I fixed my solution from earlier!

 

[chackoaltes]

Donna was 21 when her daughter was born. If Donna's daughter is 9 years old, that means Donna is 30. In 6 years Donna will be 36 and her daughter will be 15. 36 is 6 more than 15x2=30.

Thanks for your response! Silly mistake on my part

 

[chackoaltes]

Sorry, the answer is 9, thanks to BullGator1004! We can't forget to account for the fact that the daughter will age too lol! I did use the Math Destroyer, I did 16 of the 18 tests I think. I don't think there is a comprehensive list of mistakes unfortunately, sorry. This was just a tricky question, with a really easy mistake to make. I fixed my solution from earlier!

Haha can't believe I didn't see that. Tried working the problem for awhile before I posted on here. Thanks for your help! Hmm that's weird. My version only has 11 tests

 

[artist2022]

Haha can't believe I didn't see that. Tried working the problem for awhile before I posted on here. Thanks for your help! Hmm that's weird. My version only has 11 tests

I had the 2017 version (bought it like June-July of last year)! I guess they must have cut it down in the 2018 version.