# Aptitude - Square Root and Cube Root - Discussion

### Discussion :: Square Root and Cube Root - General Questions (Q.No.10)

10.

 If 5 = 2.236, then the value of 5 - 10 + 125 is equal to: 2 5

 [A]. 5.59 [B]. 7.826 [C]. 8.944 [D]. 10.062

Explanation:

 5 - 10 + 125 = (5)2 - 20 + 25 x 55 2 5 25

 = 5 - 20 + 50 25

 = 35 x 5 25 5

 = 355 10

 = 7 x 2.236 2

 = 7 x 1.118

 = 7.826

 Mannoj Kumar said: (Jun 12, 2011) Another method =sq5[ 1/2 - 10/5+ 5] =2.236[ 0.5 -2 + 5] =2.236 * 3.5 =7.82600

 Anuj said: (Jul 30, 2011) How you calculate 10/5 ?

 M.V.Krishna/Palvoncha said: (Sep 11, 2011) Hello Anuj. root=r. Given (r5/2)-(10/r5)+r125. 10/r5 = 2*5/r5 = 2r5. r125 = 5r5 (r5/2)-2r5+5r5 (r5/2)+3r5 (r5+6r5)/2 7r5/2 Subst. given r5 value we get 7.826. Hope you understood.

 Radhika said: (Apr 16, 2012) Why we multiply with squreroot 5 on both sides.

 Avinash said: (Mar 22, 2014) rt5/2 - 10/rt5 + rt125. Just put value of rt5 and calculate. 2.236/2 - 10/2.236 + 5*2.236 = 7.826. It's simple.

 Tejas said: (Oct 2, 2014) How it come 2 root 5?

 Shradha said: (Aug 31, 2015) No need to multiply root five to both side.

 Kanchan said: (Jan 17, 2016) How to solve root?

 Vipinkumar said: (Jul 23, 2016) You are right @Mannoj Kumar. @Anuj. If we take common term sqrt(5) from each term so that we get; In first term: sqrt 5[ 1/2 ]. In second term: sqrt5 [10/((sqrt5)/sqrt5)] = sqrt5[10/(sqrt5 * sqrt5)] = sqrt5[10/5]. In third term: sqrt5[(5 * sqrt5)/sqrt5] = sqrt5. In these three terms, sqrt5 is common and take it outside the bracket and apply it in the expression(question)so we get. = sq5[ 1/2 - 10/5 + 5]. = 2.236[ 0.5 -2 + 5]. = 2.236 * 3.5. = 7.82600.

 Kongkon said: (Feb 18, 2017) I don't understand. Can anyone explain me please?

 Sri Satya Kanamarlapudi said: (May 31, 2018) It can be also rewritten as (√(5) √(5)/2) - (2*√(5)√(5)/√(5))+(5*√(5)). √(5)/2 - 2√(5) +5√(5). 7√(5)/2 = 7.826.