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27*29 = __________ (calculate without direct calculation).(a) 783(b) 753(c) 763(d) 793I had been asked this question by my school teacher while I was bunking the class.My question comes from Factorisation of Polynomials and Algebraic Identities in division Polynomials of Mathematics – Class 9 |
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Answer» CORRECT ANSWER is (a) 783 The best explanation: We know that (a+b)*(a+c) = a^2 + (b+c)a + bc 27*29 can also be WRITTEN as (25+2)*(25+4) Now using above identity, 27*29 = (25+2)*(25+4) = 25^2 + (2+4)25 + (4)(2) = 625 + 6(25) + 8 = 625 + 150 + 8 = 783. |
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