About this video
The cost of entering a hospital raffle is given by the expression 5t + 3, where t is the number of tickets. Evaluating means replacing t with a number and then following the order of operations, multiplying before adding. For 1, 8 and 10 tickets the cost is 8, 43 and 53 dollars.
You'll be able to
- evaluate an expression like 5t + 3 by substituting a value for the variable.
- use the order of operations, multiplying before adding.
- explain what the variable stands for in a real situation.
Key words
- expression
- A maths phrase with numbers, variables and operations, like 5t + 3.
- variable
- A letter that stands for a number that can change, like t for the number of tickets.
- evaluate
- To work out the value of an expression when the variable is a given number.
- order of operations
- The rules for which calculation to do first; multiplication comes before addition.
Transcript
A local hospital is holding a raffle as a fundraiser. The individual cost of participating in the raffle is given by the following expression-- 5t plus 3, or 5 times t plus 3, where t represents the number of tickets someone purchases. Evaluate the expression when t is equal to 1, t is equal to 8, and t is equal to 10.
So let's first take the situation where t is equal to 1. Then this expression right over here becomes-- and I'll use that same color-- becomes 5 times 1. 5 times 1 plus 3. 5 times 1 plus 3, and we know from order of operations, you do the multiplication before you do the addition.
So this will be 5 times 1 is 5 plus 3, and then this is clearly equal to 8. Now let's do it when t is equal to 8. So when t is equal to 8, this expression becomes-- and I'll do the same colors again-- 5 times 8 plus 3. Same color of green. And once again, 5 times 8 is 40, and then we have the plus 3, there so this is equal to 43.
And so we have the last situation, with t is equal to 10. I'll do that in blue. So we have 5 times 10. So 5t is 5 times 10. Instead of a t, put a 10 there. 5 times 10 plus 3. That's a slightly different shade of green, but I think you get the idea. 5 times 10 is 50.
We do 50, and then we're going to have to add 3 to that, and that is equal to 53. And we're done.
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