Quantitative Aptitude
SURDS AND INDICES MCQs
Surds & Indices, Indices And Surds, Power
Sol. `(x^-1 - 1)/(x - 1)`
= `(1/x - 1)/(x - 1)`
= `(1 - x)/x xx 1/(x - 1)`
= `- 1/x`
Hence , the required quotient is `- 1/x`
Sol. `(256)^0.18 xx (16)^ 0.18`
= `[(16^2)^0.16 xx (16)^0.16]`
= `(16)^(2 xx 0.16) xx (16)^0.18`
= `(16)^0.32 xx (16)^0.18`
= `(16)^(0.32 + 0.18)`
= `(16)^0.5` = `(16)^(1/2) = 4`
Sol . `(.00032)^(3/5)`
= `(32/100000)^(3/5)`
=`(2^5/10^5)^(3/5)`
= `{(2/10)^5}^(3/5)` = `(1/5)^(5 xx 3/5)` = `(1/5)^3` = `1/125`
Sol . `(8/125)^-(4/3)`
= `{(2/5)^3}^-(4/3)`
= `(2/5)^{ 3 xx (-4)/3}`
= `(2/5)^-4`
= `(5/2)^4` = `5^4/2^4` = `625/16`
Sol . `(1024)^-(4/5)`
= `(4^5)^-(4/5)`
= `4^{5 xx (-1)/5}`
= `4^-4` = `1/4^4`
= `1/256`
Sol. `(27)^(2/3)`
= `(3^3)^(2/3)`
= `3^(3 xx 2/3)`
= `3^2` = 9.
`x = 5 + 2sqrt(6) = 3 + 2 + 2sqrt(6) = (sqrt(3))^2 + (sqrt(2))^2 + 2 xx sqrt(3)xxsqrt(2) = (sqrt(3) + sqrt(2))^2`
Also `, (x - 1) = 4 + 2sqrt(6) = 2(2 + sqrt(6)) = 2sqrt(2)(sqrt(2) + sqrt(3))`
`:.` ` (x - 1)/sqrt(x) = (2sqrt(2)(sqrt(3) + sqrt(2)))/((sqrt(3) + sqrt(2))) = 2sqrt(2)`.
L.C.M. of 2, 3, 4 is 12
`sqrt(2) = 2^(1/2) = 2^((1/2 xx 6/6)) = 2^(6/12) = (2^6)^(1/12) = (64)^(1/12) = root12(64)`
`root3(3) = 3^(1/3) = 3^((1/3 xx 4/4)) = 3^(4/12) = (3^4)^(1/12) = (81)^(1/12) = root12(81)`
`root4(4) = 4^(1/4) = 4^((1/4 xx 3/3)) = 4^(3/12) = (4^3)^(1/12 )= (64)^(1/12) = root12(64)`
Clearly, `root12(81), i.e. , root3(3) ` is the largest.
`2^x = 4^y = 8^z hArr 2^x = 2^(2y) = 2^(3z) hArr x = 2y = 3z`
`:. (1)/(2x) + (1)/(4y) + (1)/(6z) = 24/7 hArr (1)/(6z) + (1)/(6z) + (1)/(6z) = 24/7`
`hArr (3)/(6z) = 24/7 hArr z = (3/6 xx 7/24) = 7/48`
`a^1 = c^z = (b^y)^z = b^(yz) = (a^x)^(yz) = a^(xyz) :. xyz = 1. `