Test Your Logic and Algebra Skills
This was in Sunday’s Parade (“Ask Marilyn” section) and was fun to work out. Try it yourselves and see how much you remember.
A number has five different digits, none of which is 0: (a) The first plus the second equal the third digit; (b) the third times 2, plus the second, equals the fifth; (c) the second times 2 equals the first; (d) the first times 4 equals the fourth; and (e) the fourth minus the second equals the fifth. What is the number?
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Doug
Okay, no one got the correct answer so here’s how I solved it.
I started by drawing it out which always helps me “see” what I’m trying to solve. With what we know initially, here’s how it looks for a, b, c, d, and e respectively: [bX2] [ ? ] [a+b] [aX4] [(cX2) or (d-b)].
So beginning with the unknown b, I first tried “2”. That made a=4 but made d=16, too large (needs to be a single digit). So I tried making b=1. That made a=2, c=3, d=8 and e=7 which matched all the criteria. So the answer is 21387.
Marilyn has a much longer but more detailed answer on Parade’s site if you want to follow her reasoning. Thanks to all who that tried ( or guessed). I’ll post more of these from time to time.
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Reader Comments (8)
This will take me some time. I'll get back to you.
98765?
You're kidding, right?
52971?
I will wait for my son to get home. He can probably figure it out. Math wasn't my best subject.
21354.
Oh sure, easy for you to say.
Too bad you posted the answer. I was right on the verge of solving the problem. Oh well, maybe next time.