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  • Question
  • If a + b + c = 13, a2+b2+c2=69 then find the ab + bc + ca :


  • Options
  • A. 10
  • B. 30
  • C. 50
  • D. 70

  • Correct Answer
  • 50 

    Explanation

    a + b + c 2 = a 2 + b 2 + c 2 + 2 a b + b c + c a

    2 a b + b c + c a = a + b + c 2 - a 2 + b 2 + c 2 = 169 - 69 = 100 = a b + b c + c a = 50


  • More questions

    • 1. Choose the odd word/letters/number/number pair from the given alternatives.

    • Options
    • A. MPS
    • B. WZC
    • C. FHJ
    • D. ADG
    • Discuss
    • 2. The Shopkeeper increased the price of a product by 25% so that customer finds it difficult to purchase the required amount. But somehow the customer managed to purchase only 70% of the required amount. What is the net difference in the expenditure on that product?

    • Options
    • A. 10% more
    • B. 5% more
    • C. 12.5% more
    • D. 17.5% more
    • Discuss
    • 3. A merchant marked cloth at Rs. 50/metre . He offers 2 successive discounts of 15% and 20%. The net price/metre is

    • Options
    • A. Rs. 32.50
    • B. Rs. 42.50
    • C. Rs. 34.00
    • D. Rs. 40.00
    • Discuss
    • 4. A man gains 15% by selling a calculator for a certain price. If he sells it at the triple the price, then what will be the profit percentage?

    • Options
    • A. 125
    • B. 175
    • C. 225
    • D. 245
    • Discuss
    • 5. Choose the odd word/letters/number/number pair from the given alternatives.

    • Options
    • A. 165
    • B. 792
    • C. 852
    • D. 671
    • Discuss
    • 6. A number X is mistakenly divided by 10 instead of being multiplied by 10. What is the percentage error in the result?

    • Options
    • A. -99%
    • B. +99%
    • C. -100%
    • D. +100%
    • Discuss
    • 7. A fair six-sided die is rolled twice. What is the probability of getting 4 on the first roll and not getting 6 on the second roll ?

    • Options
    • A. 1/36
    • B. 5/36
    • C. 1/12
    • D. 1/9
    • Discuss
    • 8. A person sold his pen for Rs 24 and his profit percentage was numerically equal to the cost price. What was the cost price (in Rs) of the pen?

    • Options
    • A. 12
    • B. 14
    • C. 16
    • D. 20
    • Discuss
    • 9. What is the value of 2+2+2+2.......

    • Options
    • A. 1
    • B. 2
    • C. 3
    • D. 4
    • Discuss
    • 10. Find out the odd word/letters/number/number pair from the given alternatives.

    • Options
    • A. 82
    • B. 75
    • C. 64
    • D. 31
    • Discuss


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