Sally owns a small business which produces hand-crafted jewellery. The materials used to create a necklace cost €1.50 on average. She pays her staff €5.40 an hour. For a standard piece of jewellery she charges 70% more than it costs to produce.
To make a particular Italian-style glass necklace it takes 30 minutes. How much does she sell this single necklace for?
Determine what they are trying to ask, and what you will need to solve it
Eliminate any non-essential information
Draw a picture, graph, or equation
In moments of high stress like exam taking, always work with the paper they give you to avoid careless mistakes.
Solve.
First let’s take our givens:
Material cost: €1.50
Staff cost: €5.40 /hour
Time to make necklace: 30 min
Price of necklace: 70% more than production cost
Approach: find the cost per necklace, take 70% of the cost, and add it to the cost per necklace in order to find the selling price. Why? Because we are looking for 170 % of the necklace price since it is the production cost (100%) + 70% extra.
So:
Cost of labour: Staff cost €5.40 /hour but can make a necklace in 30 min, therefore,
(€5.40 /hour)(0.5 hours) = €2.70
Total cost of necklace = labour + materials
Total cost of necklace = $€2.70 + €1.50
Total cost of necklace = €4.20
Find 70% of €4.20
Since this problem expects us to solve it without a calculator, we can use a useful trick where we divide up the number we are working with. We all know that 70% of €1.00 = €0.70. We have €4 here so we can do $(€0.70)(4) = €2.80.
Now all we have to do is the same thing for the cents. 70% of €0.10 = €0.07. We have €0.20 so we can do $(€0.07)(2) = €0.14
Now we can add them together to find 70% of €4.20
€2.80 + €0.14 = €2.94
Find the selling cost of the necklace:
Selling cost = total cost to make necklace + 70% of total cost to make necklace
Selling cost = €4.20 + €2.94
Selling cost = €7.14
\fcolorbox{red}{grey!30}{Therefore the answer is C, $€7.14$}