# Aptitude - Square Root and Cube Root - Discussion

Discussion Forum : 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
5.59
7.826
8.944
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

Discussion:
11 comments Page 1 of 2.

Sri Satya Kanamarlapudi said:   5 years ago
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.

Kongkon said:   6 years ago
I don't understand. Can anyone explain me please?

Vipinkumar said:   7 years ago
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.

Kanchan said:   7 years ago
How to solve root?

No need to multiply root five to both side.

Tejas said:   8 years ago
How it come 2 root 5?

Avinash said:   9 years ago
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.

Why we multiply with squreroot 5 on both sides.

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.