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# Easy Surds help! C2 question! watch

1. Hey guys. I feel a little embarrassed asking this, but could anyone help me in simplifying this surd:

20√2 / √5

Someone take me step by step through this so I get to 4√10
2. (Original post by James A)
Hey guys. I feel a little embarrassed asking this, but could anyone help me in simplifying this surd:

20√2 / √5

Someone take me step by step through this so I get to 4√10
Rationalise the denominator.
3. What do you do when you have a surd as the denominator? Is this really C2?

Edit: ^The guy beat me to it.
4. Times the numerator and the dominator by root 5

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5. Not sure I'm a GCSE student but ill give it a go. So
20√2 / √5

First times by
√5/√5 so you get 20√2√5 over 5. Then √2 x √5 = √10 so now you have 20√10 over √5 x √5 which = 5. So 20√10 / 5 . Then divide by 5 to get 4√10
6. (Original post by usycool1)
Rationalise the denominator.

(Original post by QuantumSuicide)
What do you do when you have a surd as the denominator? Is this really C2?

Edit: ^The guy beat me to it.

Well I'm retaking C2 for the first time. Last time I took this exam was back in june 11. Also, this was part of a trig question, and rather than using my calc to work out the surds, I thought it would be more practical to figure out why exactly the answer is 4√10.

Also, first time I've touched A-level maths since C4 last june!

Times the numerator and the dominator by root 5

Posted from TSR Mobile
Just to clarify to all, I do (20√5 * √5) / (√5 * √5)

?
7. (Original post by James A)
Just to clarify to all, I do (20√5 * √5) / (√5 * √5)

?
It should be 20√2 (I presume that was a typo).

But yes, you have the right idea.
8. (Original post by usycool1)
It should be 20√2 (I presume that was a typo).

But yes, you have the right idea.

I understand now

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