mathematics

[Silent Hunter]

hey people ............... i wanted to know how to answer 8(C) of oct 2006 paper 1

it may seem a simple question , but i want a proper answer to it cuz i couldn't understand it :?

 

[izzahzainab]

angle B is given as 42. that is an acute angle, to find its reflex angle (greater than 180), simply substract 42 from 360. this way u'll get the angel outside the triangle but look closely.... it is still angle B!!
hope u get it

 

[Silent Hunter]

thanks but isnt the question regarding prime factors and cube numbers etc?

 

[soumayya]

360 = 2^3 * 3^2 * 5
Since 360k is a cube number,
360k = 2^3 * 3^3 * 5^3
Comparing 360k wiz 360,
k = 3 * 5^2 = 75

Hpe zat hlps...

 

[SalmanPakRocks]

@Soumayya can you please explain it again ??

 

[abcde]

For 360 k to be a cube number, all its prime factors MUST AT LEAST be raised to a minimum power of 3. As 360 = 2^3 x 3^2 x 5, you can see that for a cube number to be obtained 360 should be multiplied by 3 and 5^2. The factor 2 is already 'cubed'. That way all prime factors are 'cubed'! So k = 3 x 5^2 = 75. Now is it clear?

 

[SalmanPakRocks]

thanks !!

 

[abcde]

You're welcome