Try this TOMATO problem from I.S.I. B.Stat Entrance Objective Problem based on Series and Integers.

Series and Integers (B.Stat Objective)


The value of \(\sum ij\), where the summation is over all i and j such that \(1 \leq i \lt j \leq 10\)

  • 2640
  • 1320
  • 3025
  • none of these

Key Concepts


Series

Integers

Inequality

Check the Answer


But try the problem first…

Answer: 1320

Source
Suggested Reading

B.Stat Objective Question 81

Challenges and Thrills of Pre-College Mathematics by University Press

Try with Hints


First hint

required sum=1(2+3+4+….+10)+2(3+4+….+10)+3(4+5+….+10)+4(5+6+….+10)+5(6+7+….+10)+6(7+8+..+10)+7(8+9+10)+8(9+10)+9(10)

Second Hint

=54+104+147+180+200+204+189+152+90

Final Step

=1320

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