How do I calculate percents in my head?

For this problem, you would multiply 450 by .85, for the 15% off, and then multiply the answer by .8, for the 20%off.

move the decimal places in percentages to the left 2 places to make them decimal numbers.

ok, so you starty by taking off the 15%. so you move the decimal over 2 spots to the left to make the percentage a decimal. so 450x.15 = 67.50, so with 15% off they pay 382.50, then take off the 20%, so 382.50x.20 = 76.50, so then subtract the discount from the total 382.50 - 76.50 = 306

so they pay $306 (100% sure this is the correct answer)

People that are taking a total of 35% off are incorrect if you read the question! Its 20% off the lowest! price. So its after the 15% off.

divide by 100 then times by the desired percantage

use the sum and mutiply by100over 1

well first you have a nice easy starting number, its basically 4.5 x 100. So. 1% is equal to $4.50. You take 35 x 4.5 = 157.5 so you get a discount of 157.5.

Thats how I would calculate it.

ten percent is 45  20 percent is 90
the best way is to do this

for ten percent take off the first two numbers then for 20 30 40 50 60 70 80 90 100 etc just keep adding hence 45 plus 45 equals 90 so if its 5 percent its half of ten so it would be  22.5 because thats half of 45 now 15 is 22.5 pluse 45 so thats .............. 67.5   so now lets go to thirty five so  45 times 3   plus 22.5    45, 90  135 plus 22.5 equals  157.50

10% of 450 would be 45.  Easy right? Another half of 45 is 22.5, so 67.50 is 15% of $450.  450 minus 67.50 is 382.50. 10% of 382.50 is 38.25. Double that is 20% or 76.50.  382.50 minus 76.5 is $306.00, or the selling price of the item.

I'm assuming you can use pencil and paper during the test even if you can't use a calc.

You two guys that say the discount is $157.50 are miscalculating.  You're multiplying one discount by another and it's too much.

You're not allowed to use a calculator, but did u check if they let u use pen and paper?  I mean I haven't heard of a test where u weren't allowed to put down the numbers on paper...even on the GMAT I had that:)

Initial cost -$450.  Expensive;))))
there's a 15% sale...so the dishwasher costs  just 85% of the $450 (getting better)
after another 20% off the lowest price (discount given to employees)...the dishwasher costs 80% * (85%*450) =80/100* 85/100* $450 =80*85*450/10000 (you do the calculation:)

The best way to approach this is to start with the 15% off.   For every $100 spent, the employee gets $15 off.   So, start with $400.. that gives you 4 x $15 = $60 off the list price.   From there you take 15% off of $50 which is half of $15 or 7.50.   So, to start you have $67.50 off of $450 = $382.50.

Same for $382.50, now for every $100, take $20 off.   So, that's $60 for the first $300 and then $16.50 for the remainder ($2 for every $10).

So, the final price should be $306.

First, find out the sale price (15% off 450), then find the employee discount (20% off the sale price.)

*****************
15% off 450:
You need to know what you're PAYING, not the amount off.
100 - 15% = 85%
So, you need to find
450 * 85%

You can do this two ways...  If you can multiply decimals on paper ok, just multiply 450 * 0.85 and you'll get your answer.  ($382.50).<><><><>
The other way to do it:
Calculate 15% of 450.

15% = 10% + 5%

10% is found by moving the decimal one place to the left
so 10% of 450 is $45.

5% is going to be HALF of 10%, so half of $45 is $22.50

So, 15% of 450 = 45 + 22.50 = $67.50

That's the amount taken off the original price.

So, you have to subtract that from the original price

$450 - $67.50 = $382.50
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Now, you need to find 20% off $382.50.

One way:
100 - 20% = 80%
So...
80% of 382.50
= 382.50 * 0.8
= $306

The other way...

20% = 10% + 10%

10% of 382.50 = just move the decimal one place to the left.
So, 10% of 382.50 is $38.25

So, 20% is 38.25 + 38.25 = $76.50

Take the sale price (382.50) minus the discount (76.50)
382.50 - 76.50 = $306

There are two ways of dealing with multiple discounts:
- Chain.  The percentages are multiplied.  In the problem stated, the final price would be 80% x 85% x $400, or $272.  This is by far the most common.
- Sequential.  The percentages are applied to the original price.  Here, $400 discounted by 20% is $80 off, and $400 discounted by 15% is $60 off, for a total discount of $140, or a final price of $260.  This is seldom done, for obvious reasons.

calculating percentages without a calculator is kind of like trying to be smarter than the exercise... i'll use your example: first, the original price of the dishwasher is $450. the other information you need to solve this is 1.) the dishwasher was on sale for 15% off, and 2. ) the employee discount is 20%. (i'm going to assume that you're allowed to use scratch paper, and are competent in 8th grade math.)

because the employee discount applies to the lowest price, you need to figure out the sale price first. the easiest way to do so is by finding what 10% is, by moving the decimal one place to the left. thus, 10% of 450 is 45. to find 15%, you multiply 45 by 1.5. after you've figured out that number (67.5), subtract it from the original price. the sale price is $382.50.

now that you have the sale price, you can figure out the employee discount, which is 20% off the sale price. to find 20% of 382.50, you use the same theory as above: move the decimal one place to the left (38.25) and then multiply by 2 (76.50). after you've figured out the amount of the discount, subtract it from the sale price. the employee paid $306 for the dishwasher.

**yes, i did all of this in my head, without scratch paper... i apologize if any of it is wrong, i did it very quickly and didn't check my work, but the theory is correct, and you should be able to apply it to most problems**

First, let's figure out how much the fridge will cost with the 15% discount.  Since 15% is the part of the price he doesn't have to pay, 85% is the part of the price that is left.  85% is just another way to say 85/100, or .85.  So multiply the cost of $450 by .85 and you'll find out the amount he has to pay after the %15 off sale.  $450 times .85 is $382.50, with the use of basic multiplication.

Now do it again, with 20% instead of 15%.  Now he only has to pay 80% of the $382.50, so multiply $382.50 by .80

$306