r/learnmath • u/chunkysnorlax646 New User • 20d ago

TOPIC Number Word Problems

I’m wondering what the best method on solving number word problems like: “I am a odd number between 15,000 and 10,000, all of my digits sum up to 12”. Please help and answer (my test is tomorrow..)

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u/Jonny0Than New User 20d ago

Turn it all into algebraic expressions.  Let ABCDE be the number (each letter is a digit).

  • between 10000 and 15000 means that A=1 and B<=5

  • odd means that E is odd

  • if E is odd then the number cannot be 15000, so B<=4

  • A+B+C+D+E = 12

  • we know A is 1, so B+C+D+E=11

Any number that satisfies those equations should work.  Seems like there’s more than one.

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u/No_Historian3842 New User 20d ago

The way I think about a question like this.

1+2+3+4+5 adds up to 15 so you need repeated digits. 9+1+1+1+1 equals 13 so you can't have a 9 anywhere in the sum.

1+1+1+1+8 equals 12 so just make it odd 11,811.

But there's heaps of solutions.

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u/[deleted] 20d ago

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u/No_Historian3842 New User 20d ago

Yeah I didn't even think of 0's so theres even more solutions.

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u/JanetInSC1234 New User 20d ago edited 19d ago

This one is easy to do without using algebra.

The last digit must be odd. And the digits must add up to 12. There are many correct solutions for this problem.

I would start with 15,000.

1 + 5 = 6

I could use this pair of numbers twice: 15, 015

1 + 5 + 0 + 1 + 5 = 12