Percentage, very confused! Please help, thank you

[prometheus]

1. If a discount of 20% off the retail price of a desk saves Mark $45, how much did he pay for the desk?


A. $145
B. $160
C. $180
D. $210
E. $215

So I know the answer is C BUT I have no idea how to get there. Could someone please provide me with the formula needed in laymans terms to arrive at the correct answer please? Thank you.

 

[jsterkel]

So, what do you know?

You know the percentage that was discounted (20% off ).

You know how much the discount was ($45).

Can you write an equation for that?

If not, try to look at this the other direction. If you were working at a store, and your boss told you to give his brother a 20% discount, and the original cost was $150, how would you calculate this? Write it down. Now, can you rearrange this?

 

[burakaltr]

1. If a discount of 20% off the retail price of a desk saves Mark $45, how much did he pay for the desk?


A. $145
B. $160
C. $180
D. $210
E. $215

So I know the answer is C BUT I have no idea how to get there. Could someone please provide me with the formula needed in laymans terms to arrive at the correct answer please? Thank you.

In these types of questions for your ease

set Price=100*k

where 20 per cent of that would be obviously 20*k

set

20*k=discount ( saves )

we need to find 100*k

so multiply 2 sides by 5

Price = 100*k = 5 * discount

Easy as that

 

[prometheus]

Thank you all for your help, that clears it up nicely.

No, I didn't get the answer from my teacher, I don't have one lol!!

I am 30 and I have a numerical reasoning test to sit by the 4/09 for a Graduate programme but maths has always been my weakest subject and I never sat my maths GCSE. Stupidly, I thought I would never need it but as you get older you realise that the world revolves around math and science lol.

I got the answer by using fractions as 20% is obviously a 5th but was worried that I would get asked a question using something like 36% where the answer is not so obvious!!

Thank you all again. It is much appreciated.