Writing Expressions
What is a variable?
A LETTER that represents and unknown number.
What is a ratio?
A relationship between two numbers.
200% of the original figure.
Enlarge times two!
If a rectangle has side lengths of 2 and 3, and is enlarged by 300%, what are the new side lengths?
6 by 9
Write an expression: Bob has a certain number of cars. He added 15 cars to his collection. Define your variable.
Find 3 equivalent ratios to 4:6
2:3, 8:12, 12:18, etc.
1/5 of the original figure.
Reduce by dividing by 5
A triangle has a base of 12 and a height of 18. The ratio of this triangle to the new triangle is 3:1. What are the new base and height?
4 x 6
A gym costs $30 to join and then $6 per month after that. Write an expression to show the total cost of the membership over time. Define your variable.
m = number of months at the gym
6m + 30
For every 2 miles Mr. Denning runs, he hikes 6 miles. Write the ratio of running miles to hiking miles. Then, figure out how many miles Mr. Denning hikes if he runs 8 miles.
2:6 (or 1:3), 24 miles of hiking if he runs 8 miles.
Ratio of 1:1 new to original figure.
Doesn't change!
A circle has a diameter of 14 units, and is reduced by 50%. What is the new diameter?
7 units
Cindy's training plan is to run a certain amount of miles for each of the next 4 days, then 3 miles, then 6 days of running 2 miles. Write an expression to summarize this training plan. Define your variable. Figure out how many total miles she runs if she runs 5 miles each of the first 4 days.
x = number of miles for each of the first four days
Expression: 4x + 3 + 6(2)
Evaluation: 4(5) + 3 + 6(2) = 35 miles
For every 8 points Mr. Denning scores in his basketball game, his wife allows him to eat 3 pieces of pizza. Mr. Denning is a baller, and scores 40 points in the game. How many pieces of pizza did Mr. Denning eat?
15 pieces!
Ratio of 1:4 original to new figure.
Enlarge by a scale factor of 4.
A trapezoid has a base of 9 units. It is multiplied by a scale factor of 3.5. What is the new base?
31.5 units
Croakie has a new routine! He starts by jumping 8 feet to the right, then 3 feet to the left, then 4 "super jumps" to the right, then one more jump to the left 1 foot. Define your variable. Write and expression to represent this routine. Figure out how long a super jump is if the total routine is 20 feet.
Expression: 8 - 3 + 4s - 1
Each super jump is 4 feet!
15 of them are green.
Multiply by a scale factor of 1/4
Reduce!
Mr. Denning has a rectangular garden in his back yard. He wants to keep the same relationship between sides, but make the garden 25% of its current size. Right now, it measure 136 feet wide and 208 feet long. What should the reduced dimensions of the garden be?
34 feet wide and 52 feet long