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Mathematical Reasoning Videos 30 videos

CAHSEE Math 1.1 Mathematical Reasoning
228 Views

CAHSEE Mathematical Reasoning: Drill 1, Problem 1. Based on this information, which of the following can be determined?

CAHSEE Math 1.2 Mathematical Reasoning
185 Views

CAHSEE Math Mathematical Reasoning: Drill Set 1, Problem 2. Which of the following should be the most appropriate first step in solving the equation?

CAHSEE Math 1.3 Mathematical Reasoning
183 Views

CAHSEE Math Mathematical Reasoning: Drill 1 Problem 3. Which of the following is the correct order of steps?

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CAHSEE Math 3.5 Mathematical Reasoning 227 Views


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Description:

Mathematical Reasoning Drill 3, Problem 5. Because of the way Cheryl made her estimation, her estimate will be what?

Language:
English Language

Transcript

00:02

And here's your shmoop du jour...

00:04

Cheryl is just learning to ride a bike. She’s nervous, and wants to start small.

00:08

REALLY small. Her bicycle wheel has a diameter of 18.1 inches.

00:13

Using the formula for the circumference of a circle, 

00:16

C = πd, where d is the diameter, and C is the circumference…

00:20

…she estimates that, with one full revolution of the wheel… which is as far as she wants to go…

00:25

she travels a distance of about 54 inches, or 4.5 feet.

00:30

Because of the way she made her estimation, her estimate will be... what?

00:35

And here are the potential answers...

00:40

OK, so this question is asking us about estimation, and how exact Cheryl's estimation is compared

00:46

to the exact distance.

00:48

We estimate all the time...what score we're going to get on the next math test…

00:52

…how many marshmallows we can fit in our mouths, and so on.

00:55

Using the circumference formula, C equals pi times diameter…

01:00

…Cheryl must have rounded down the value of π to 3 and 18.1 to 18…

01:07

…so then we just arrive at the value of C = 3 times 18 which is 54.

01:14

Because she rounded down for both pi and the diameter, the product or circumference will

01:18

be an underestimate of the exact distance.

01:21

Answer is A.

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