Math destroyer Mistake?

[spoog74]

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test #5 problem 13

Two work crews, Crew a and crew b start digging a 300-oot tunnel through a mountain but working toward each other from opposite sides. If crew a digs at 12 feet a day and crew b digs at 18 feet a day, how many feet will crew a have dug when the two crews meet?

I got 120 yet the answer according to the destroyer is 180.....


Anyone with some insight?

 

[dentalWorks]

I think you are correct.

I got 10 days as the number of days to get the tunnel complete.

10 * 12 = 120 feet for A
10 * 18 = 180 feet for B

 

[herkulease]

Its an error.

There are other errors through out Math destroyer at least on the 2010 edition. If you have the 2011 edition, I'm surprised he didn't go back and fix them.

I did test 10 today. #26 is another error. Either the question is written wrong or the answer choices provided are wrong. 3 valid choices for 1 one, 2 for another.

I seriously wish they'd put up a corrections list.

 

[dentalWorks]

sad thing is....

when I did some 2009 tests... they had similar errors and I think that tunnel one is still an error.

 

[YoonS]

I had a same problem with you. It's definately 120

 

[wired202808]

I had a same problem with you. It's definately 120

how do you even do this problem? I understand the total rate is 30 and thus they would finish the tunnel in 10 days, but why would they meet at 120 ft? is it because crew A aka 12 is the slowest and hence they would not be able to meet before 10 days?

 

[wenjie1988]

how do you even do this problem? I understand the total rate is 30 and thus they would finish the tunnel in 10 days, but why would they meet at 120 ft? is it because crew A aka 12 is the slowest and hence they would not be able to meet before 10 days?

It's asking for how many feet crew A will have dug when the 2 crews meet. They will meet when they finish digging the 300 feet together. It takes them 10 days together to finish digging. Since the rate of crew A is 12 feet per day, after 10 days, crew A digs 120 feets.

 

[datstudy1]

Hey, do you know of any other errors in destroyer or if someone has a list of known wrong answers from the 2011 destroyer?
Thanks.

 

[toothhornet88]

Hey, do you know of any other errors in destroyer or if someone has a list of known wrong answers from the 2011 destroyer?
Thanks.

That's the only one to my knowledge! I went through it 1.5x times