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# Maths Rationalising Question Watch

1. Hi, how would I answer this question? Rationalise the denominator: The square root of 3 over the square root of 15. I've had a look at the right answer and it's the square root of 5 over 5. How would you get this answer?
2. Well rationalising would mean to get rid of any surds in the denominator, try multiplying the whole fraction by root15 and simplifying from there to try reach the answer.
3. (Original post by JN17)
Well rationalising would mean to get rid of any surds in the denominator, try multiplying the whole fraction by root15 and simplifying from there to try reach the answer.
I tried simplifying root 45 over 15 and I got 3*root 5 over 15.
4. (Original post by HurtfulHarold)
I tried simplifying root 45 over 15 and I got 3*root 5 over 15.
Yes - now simplify by dividing numerator and denominator by 3,
5. (Original post by HurtfulHarold)
I tried simplifying root 45 over 15 and I got 3*root 5 over 15.
Yeah, so just divide the fraction by 3 , always look for common factors in the numerator&denominator.

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