Solution Key for mathematics mock test (specifcially question 6)

[prav...@gmail.com]

Dear Course team,

Will you please make available the solution detail for the maths mock test?

Similar to other weekly tests?

Specifically interested in Q6 and the correct quadratic modeling for the problem.

Thanks and regards,

Praveen

[Malabika Guha Mustafi]

For question 6, there are 2 approaches.

1) Considering both selling price and cost price. Take the difference and make an equation for profit.

Present selling price =5 , cost price= 3 [2 Rs profit], after x Rs increase, new selling price= x+5

Then the equation is 

P= (20000-2000x)(5+x) - (20000-2000x)(3).

Then compute x (vertex, -b/2a)

2) The second approach and easy to compute solution as follows:

Consider only profit portion and make an equation.

P= (20000-2000x) *( 2+x) [ since the profit is now 2 and after x price increase it will be 2+x]

compute x (vertex , -b/2a)

[prav...@gmail.com]

Ok thanx,

So the assumption is to say that the CP stays as it is...which means if the SP is increased by x then the new profit is the full (2+x) and there is no linear relation between SP and CP (eg SP = 5/3 CP) which didnt occur to me (rather say was not trivial practically).

With that assumption, we can also directly model for the new SP as x:

maxProfit = maximise((x-3)*2000(10-(x-5))) as SP increase is (x-5), which is the rate of subscription loss.

--> maximise ((x-3)(15-x))

-b/2a directly gives 9.

But again my question was because I didnt guess the CP remaining constant...:-(

Thanks,

Praveen

[Malabika Guha Mustafi]

Actually last time in practice session , c.p was not constant. But in mock it is considered as constant.

[jothivarshini shanmugaraja]

hi, i can't understand this step can someone explain it to me?

compute x (vertex , -b/2a) 

thanks again 

[Malabika Guha Mustafi]

@Jothivarshini,

Sorry, the presentation was not right.
compute x (vertex , -b/2a)  it means compute the x value at vertex which is -b/2a.