A number theory problem by Jack Rawlin

Number Theory Level pending

You are told that a for a three digit number A B C \overline{ABC}

A B C C B A = 198 \overline{ABC} - \overline{CBA} = -198

A B C + B = 327 \overline{ABC} + B = 327

D = ( A + 2 B + 3 C ) 14 D = (A + 2B + 3C) - 14

Find D B A C 5 \frac {\overline{DBAC}}{5}


Details and assumptions

  1. A B C = 100 A + 10 B + C \overline{ABC} = 100A + 10B + C

  2. A A , B B , C C and D D are all positive integers under 10 10 .

  3. A > 0 A > 0

  4. D B A C 5 \frac{\overline{DBAC}}{5} is an integer.


The answer is 1647.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Jack Rawlin
Jan 4, 2015

We know that

A B C C B A = 198 \overline{ABC} - \overline{CBA} = -198

A B C = 100 A + 10 B + C \overline{ABC} = 100A + 10B + C

So the equation can be re-written to be

99 A 99 C = 198 99A - 99C = -198

Which then gives us an equation for A A

A = C 2 A = C - 2

Next we should find out A A and C C so since we know that

D B A C 5 \frac{\overline{DBAC}}{5}

is an integer we can conclude that C C is a multiple of 5 5 below 10 10 so it can only be 0 0 or 5 5 so let's put those values into the equation we have for A A to see which value works

A = ( 0 ) 2 = 2 A = (0) - 2 = -2

That doesn't work since we know that A > 0 A > 0

A = ( 5 ) 2 = 3 A = (5) - 2 = 3

So A = 3 A = 3 and C = 5 C = 5 .

Onto the second equation given

A B C + B = 327 \overline{ABC} + B = 327

100 A + 10 B + C + B = 327 100A + 10B + C + B = 327

100 ( 3 ) + 11 B + ( 5 ) = 327 100(3) + 11B + (5) = 327

11 B = 327 305 11B = 327 - 305

B = 2 B = 2

We now know A A , B B and C C , but what about D D

D = ( ( 3 ) + 2 ( 2 ) + 3 ( 5 ) ) 14 = 8 D = ((3) + 2(2) + 3(5)) - 14 = 8

So D B A C = 8235 \overline{DBAC} = 8235

Which then means that

D B A C 5 = 1647 \frac{\overline{DBAC}}{5} = 1647

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...