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  1. If a = 4011 and b = 3989 then value of ab = ?
    1. 15999879
    2. 15899879
    3. 15989979
    4. 15998879
Correct Option: A

Given , a = 4011, b = 3989
∴  ab = 4011 × 3989
ab = (4000 + 11) (4000 – 11)
ab = (4000)2 – (11)2
ab = 16000000 – 121
ab = 15999879


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