How do you work this out?

The sales price of a car is $12,590, which is 20% off the original price. What is the original price?





A. $14,310.40


B. $14,990.90


C. $15,290.70


D. $15,737.50


E. $16,935.80





The answer is D, but I don't know why. Could someone help me?How do you work this out?
If $12,590 is 20% off of the original price, that mean's that by itself, it is 80% of the original price. Since 80% is 80/100, multiplying it by its reciprocal, 100/80 (or 5/4) would give you 100% so 12,590 x 5/4 = 15,727.50





hope this helps, good luckHow do you work this out?
Kinda like doing a tip in reverse.


Only use $, forget cents.





Move the decimal point one space, gives you 10%, double it to get 20%. This is the discount off the price, which you'd add to the $12590





Randomly picking A, you see that you would be off by 2863, almost $3000. You could also randomly pick any of the above, either right or wrong, but if you pick a, b, or E first by some reason, you can see how far you'd be off.





So A, B and D are out (1st too low, last too high)





D would be closest to the $3000 discount, but if you check your work, 15737.50 x .20 = 3147.5. Add that discount to sale price of $12590, and you come back with a match, being $15737.50.








Also, tests TEND to use middle answers, c most common, then D or B if there are 5 choices. So if you are short on time, try those first.





And if you HAVE to quess, short on time, pick the same letter over and over, again, C will be the statistically most common correct answer. So in general, try C 1st, see that you are close, and then go to D.
Let ';x'; equal the original price.





So the equation is:


x = $12,590 + .2x





Now solve for x:


x = $12,590 + .2x


x - .2x = $12,590


.8x = $12,590


x = $12,590/.8


x = $15,737.50





Good luck in your studies,


~ Mitch ~