Math Is Fun Forum

Q2...   in july,the prize of sugar increased by 10% , in August,it is declined by 20% and in september,it is increased by 10%,What is final Decline in prize
a.3.2%
b.Zero
3.20%
c...None

The answer is "a"

Explanation:
First let's assume this is the price for a 30 pound bag of sugar, which we will just call a bag. 

Say the price of a bag, in June was $100.00. Come July and the price goes up 10%. Ten percent of 100.00 means 10 per 100; or ten out of every hundred things.  Ten cents out of one hundred cents, is 10 cents out of a dollar so 10 cents is ten per cent of a dollar.  Just like ten dollars are ten percent of a one hundred dollars bill.
So you add 10% of $100.00, to $100.00 you get ...
   
          $100.00  + $10.00 = $110.00   

$110.00  becomes the new price for the same bag of sugar, after the July increase.

To obtain the new price,  you need to find out what 10% of the price is.
remember 10 cents = 10% of a dollar, if you look at the display at the store, there is a decimal point, and after the decimal point the cents are shown. 10 cents are shown as $ .10

To get 10% of any number, just multiply the number times 0.10
To get 20% of any number, just multiply the number times 0.20
To get 25% of any number, just multiply the number times 0.25

To obtain the new price you multiplied 100 x 10% = 10.00. Then added the result to the $100.00

But in August, the price goes down by 20%. That is 20 cents out of every dollar.  So now you have to deduct, which means subtract, 20%f of the new price. If your bag during July sold for $110.00, after the August decrease, the same bag, will sell for 20% less.

Lets find 20% of $110.00  by multiplying $110.00 times 0.20

          110.00 x .20 = 22.00

So the new price in August is:

         $110.00 - $22.00 = $88.00 price after the August reduction in price.

Come September, an increase of 10% of $88.00.

         $ 88.00 x 0,10 =  $8.80

So the new price is:

         $ 88.00 + $8.80 = $96.80 

With this information we can answer the question:

If sugar was $100.00 a bag before any of this, and sugar is now $96.80 per bag,
The price definitely declined, but, by what percentage?

         $100.00 - $96.80 =  $3.20

if it was $100.00 a bag, and it declined by  $3.20 per bag
the decline is 3.2 dollars out of 100 dollars which is answer "a".