Question

    The average of first two numbers and last two numbers of

    a set of six numbers is 70 and 45 respectively. If the overall average of all six numbers is 65, find the average of third and fourth number.
    A 50 Correct Answer Incorrect Answer
    B 80 Correct Answer Incorrect Answer
    C 60 Correct Answer Incorrect Answer
    D 35 Correct Answer Incorrect Answer

    Solution

    Let the six numbers be a, b, c, d, e, f. a + b = 2  70 = 140 ....................... (i) e + f = 2  45 = 90  ........................ (ii) a+ b + c + d + e + f = 6  65 = 390 ........................(iii) We get the sum of third and fourth digit by subtracting (i) and (ii) from (iii) a+ b+ c + d + e + f – a – b – e  - f = 390 – 140 – 90 =160 ∴ c + d = 160  ∴ Required average =    = 80

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