Proportion

Question

y is inversely proportional to x^2.Here is the table in the question:

x   2      4      b

y   10     a     1.6

 

Please find a and b

Answer 1

From the table first column, y is 5 times x (5*2=10). The same proportional relation exists between the numbers in the other two columns, so a=5*4=20 and 5b=1.6, so b=1.6/5=0.32.

The other way of doing this is to look at the rows instead of the columns. In the x row 4 is twice 2 and in the y row a would be twice 10=20. And b/2=1.6/10=0.16, so b=2*0.16=0.32.

In the light of further info, i.e., y inversely proportional to x^2, we can write y=A/x^2, and substitute y=10 and x=2, from which A=40, A being the constant of proportionality. Therefore a=40/16=5/2=2.5 and 1.6=40/b^2 so b^2=40/1.6=25, therefore b=5.

Comments

Can you please recheck this question I stupidly left out some information, this is now fixed.