Cpt quantitative aptitude problem

CPT 18403 views 6 replies

 

please tell me the correct answers and explain it too how you get those figures...thanx in advance :)

The ratio compounded of 4:9, the duplicate ratio of 3:4, the triplicate ratio of 2:3 and 9:7 is

  1. 2:7
  2. 7:2
  3. 2:27
  4. None of these

P, Q and R are three cities. The ratio of average temperature between P and Q is 11:12 and that between P and R is 9:8. The ratio between the average temperature of Q and R is

  1. 22:27
  2. 27:22
  3. 32:33
  4. None of these

If 2s:3t is the duplicate ratio of 2s-p: 3t-p then

  1. P2(P2 is square of P) = 6st
  2. P = 6st
  3. 2P = 3st
  4. None of these
Replies (6)

1. 4* 9* 8* 9 =2592 multiply : 9*16*27*7 =27216 thus ratio is : 2592:27216 =2:21 

 
 
2 P,Q,R are 3 cities, the ratio of temperature of P,Q is 11:12, and P and R 9:8, what is the ratio of Q & R is ? P = 11 * 9 = 99 cross multiply P11


 
3.as 2s : 3t is the duplicate  ratio of 2s - p : 3t - p,
so we can write it as...
                              2s : 3t = ( 2s - p : 3t - p)2
                       =>   2s : 3t = 4s2 + p2 -4sp : 9t2 +p2 -6p
                       =>   2s(9t2 +p2 -6p) = to R 8 = 88, cross multiply P 9 to Q 12, = 108 thus P:Q:R= 99:108:88 Q:R=108:88 = 27:22 
    3t (4s2 + p2 -4sp)
                       =>   18st2 +2sp2 -12sp = 12ts2 + 3tp2 -12tsp
                       =>    p2 (2s - 3t)  =  6ts (2s - 3t)           //  -12sp cancel
                       =>    p2 = 6ts
 

 

In the first question why did we take 9:7 ratio where as not the triplicate of it?

https://youtu.be/QQnLM2BIonQ


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