Math question p varies jointly

Question

If P varies jointly as q and r and p=150 when q =18 and r = 5 find q when p=345 and r =9

Answer 1

P varies jointly as q and r

 

p=k* q r

 

150 =k *(18)(5)

 

150 = k*(90)

 

150/90 = k

 

5/3 = k

 

find q when p=345 and r =9

 

p=k* q r

 

345 = (5/3) * q *9

 

345 = 45 q / 3

 

1035 = 45 q

 

q=23