Consecutive Integers

Number Theory Level pending

Two sets { a n } \{a_n\} and { b n } \{b_n\} of 4 consecutive positive integers have exactly one integer in common. Let

  • A A denote the sum of the integers in { a n } \{a_n\} , which is the set with the greater numbers, and
  • B B denote the sum of the integers in { b n } \{b_n\} .

Find A B A-B .

24 12 8 it can not be detemined 20

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1 solution

Hana Wehbi
Jun 22, 2016

We can write A a n d B A \ and \ B as follows:

B : { n + ( n + 1 ) + ( n + 2 ) + ( n + 3 ) } B :\{ n + (n+1) + (n+2) + (n+3)\} and

A : { ( n + 3 ) + ( n + 4 ) + ( n + 5 ) + ( n + 6 ) } A: \{(n+3) + (n+4) + (n+5) + (n+6)\} for n > 0 n>0 .

Note that each term in the second set is 3 3 more than the equivalent term in the first set. Since there are four terms, then the total differences will be 4 × 3 = 12 4 \times 3 = 12

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