8 Maths GST & Best Buys

Introduction

Discounts

A. Read the information below:

  • To get rid of old stock (e.g. out-of-date fashions at the end of a season), store managers often reduce prices by giving discounts.
  • A discount is a reduction in price.
  • A discount can be shown as an amount in dollars. 
  • A discount can be shown as a percentage of the marked price (i.e. the price marked on the article).

B. Use the following method to find the reduced price:

         (original price) - (original price x discount percentage) = discounted price

  • For example, a 10% discount on an item marked at $120:



    10% x 120 = $12   ----->  this is the discount 



    Then subtract the discount amount from the original price:



    120 - 12 = $108    ----->  this is the discounted price

B. Watch this video to revise how to calculate a discount:

https://www.youtube.com/watch?v=1pdnLsx6tkQ

C. Practice what you have learned, by completing the examples below, in your books:

  1. Find the sale price on a hat marked $72 if a 10% discount is given.

     
  2. Decrease the amount by the percentages:

    a)  $50 by 10%

    b)  $90 by 50%

    c)  $45 by 20%

     
  3. A sale discount of 20% was offered by the music store Solid Sound. Find:

    a)  the cash discount allowed on a $350 sound system

    b)  the sale price of the system.

 

Calculating the Original Price once a Discount is Given:

A. Use the following method to determine the original price: 

  • To calculate the original price from the discounted price, use the method below:



    (Original price) = Discounted Price / (100% - discount%) 

B. Watch this video:

https://www.youtube.com/watch?v=RJmWJmoZFpg

C. Practice what you have learned, by completing the questions below: 

  1. Find the original price of a pair of shoes if the sale price is $98.00 after a 30% discount.

     
  2. A radio sells for $63, after a 40%discount. What was the original price.

  3. A new car is sold for $8,400 after a 30% discount. Find the original price of the car.

Calculating GST

A.  Read the information below:

  • GST stands for Goods & Services Tax. The GST makes up 10% of the price we pay for goods, which are most things. And services, which are people doing things for us. So, if something costs you $110, 10 of those dollars go straight to the government.

     
  • As such, when GST is included in a price, then the total price will be 110%.

    Similarly, the original price (excluding GST) is 100%.

  • The unitary method is a technique which can be used to determine GST, and can also be used for solving a problem by finding the value of a single unit, i.e., 1, (by dividing) and then finding the necessary value by multiplying the single unit value. 

  • For example, if you have a TV that costs $550 incl. GST, what is the price excluding GST?



    Using the Unitary method, we need to determine the cost of 1%, then multiply that by 100. 



    $550 = 110%   ----------> the price including GST



       รท 110



    $5 = 1%    -------------> the price of ONE UNIT



       x 100 



    = $500   ----------------> The original price (excl. GST)

B.  Practice this, by completing the questions below.

  1. The cost of a gold ring is $390 excl. GST. What is the total cost incl. GST?

     
  2. Noah wants to a desk that costs $290 before GST. Find the total cost including GST.

     
  3. Rosa plans to pay her Accountant $840 for her services, plus GST at 10%. Calculate the total cost after GST is added.

     
  4. A fan has a cost of $500 excl. GST at 10%. What is the total cost incl. GST?

     
  5. If a remote control car is $120 incl. GST:

    a) Find the GST.

    b) Find the price before the GST.

     
  6. A chair costs $150 incl. GST:

    a) Find the GST.

    b) Find the price before GST.

     

Now complete this Quiz!

https://play.kahoot.it/#/lobby?quizId=ffc1e0d9-fc65-4bab-a619-ef8aa48b78b2