Evaluating Expressions 04:03 minutes

Video Transcript

Transcript Evaluating Expressions

Let me tell you a story about evaluating expressions

Once upon a time

"Once upon a time, there lived a girl in a tower
She was there every day, hour after hour."
"Her name was Rap-Punzel,
a mischievious damsel, whose hair was a handful"

"The love of her life, Prince MC,
was in love with Rap-Punzel... as in love as can be.
They waited for the day and waited for the time
when the prince could scale the tower with a short little climb."
"But he's tired of waiting, what a waste of days.
He should evaluate expressions but he doesn't know the way"

Let's help MC Prince. At the start of this tale, Rap-Punzel’s hair is 50 inches long. Each month, it grows 5 inches." Let’s write this as an expression… 50 is the constant number in this expression, meaning it does not change. We said before that her hair grows at a rate of 5 inches per month. The number of months is the unknown quantity, which we will call x. We can also use any other variable.

Expression for the length of Rap-Punzel's hair

The number five is the coefficient of the variable. So… the expression to describe the length of Rap-Punzel's hair after a variable number of months is 5x + 50. Ok, let's use our expression to evaluate the length of Rap-Punzel's glorious hair over a period of a few months. Let’s set up a function table… When evaluating expressions, always remember to use the correct order of operations.

Calculation of further growth

After 1 month, the length of her hair is equal to 5(1) + 50, for a total length of 55 inches. After 2 months, the length is 2(5) + 50, which equals 60. Let’s fill in the table... OMG, after 6 months, Rap-Punzel’s hair is a staggering 80 inches long! But, disaster struck and Rap-Punzel discovered that her glorious hair was not so glorious after all ... - it was full of split ends. (Pause). Impulsively, ....

... she cut her hair. Now it's just 10 inches long. To keep her hair healthy, Rap-Punzel must trim her hair two inches every month. Despondent, MC Prince wondered, how much longer must he wait to be with his beloved? Let's modify our expression. 5x for the growth per month minus 2x for the trimming per month plus ten for the starting length.

Insert the right numbers

Now, simplify the expression. 3x + 10. MC Prince wondered, '...after six more months, how long will her hair be?...' Evaluate the expression, this time, letting x equal six… use the correct order of operations, 3(6) = 18; plus ten it is equal to twenty-eight. Her hair will only be twenty-eight inches long!

"Still waiting outside, MC Prince began to doubt
without Rapunzel in his life, he's like a plant in a drought
he had an idea, on which he was keen"
what's this? OH NO...he bought magic beans...

2 comments
  1. Default

    Yeaaaah paaaaaad

    Posted by Student017 13, over 1 year ago
  2. Default

    if you need to get rid of the coefficient as in 0.5x it is best to divide. so divide both sides by 0.5 and that will give you the answer.

    Posted by Ablkmannla, over 1 year ago