Geometry
Error Exterminator: _________________________________________ Per: _
Section 9.1 – 9.4 – Common Errors
Date: _____________
Mr. O made the following errors. Help him fix them since he is so forgetful sometimes.
1. Find the value of the variable x.
Mr. O’s Method
What did Mr. O do wrong?
Your Correct Method
x 2  (2)(12)
x 2  24
x  24  2 6
2. A painter leans a ladder that is 25 feet long against a house. He places it 15 feet away as it makes a safe
angle where the ladder will not fall over when he stands on it. He needs to reach a place that is 22 feet high
in order to pain that section. Will he be able to reach and paint the section?
Mr. O’s Method
I am not going to draw a picture
because I can just visualize it in my
head and set up my Pythagorean
theorem as follows:
x 2  152  252
x 2  225  625
x 2  850
x  29.155 feet
What did Mr. O do wrong?
Your Correct Method
3. Determine the type of triangle that the sides 5, 7, and 12 make.
Mr. O’s Method
12 ? 5  7 2
2
What did Mr. O do wrong?
Your Correct Method
2
144 ? 25  49
144 ? 74
144  74
Therefore it is an obtuse 
4. Find the values of x and y in the diagram shown.
Mr. O’s Method
What did Mr. O do wrong?
Your Correct Method
This one is a little tricky but I first
see that opposite the 30 is a side
with a length of 8 so that is my “A”
value. The y is opposite the 90 so
that means it is “2A” or a length of
16. Then, the x is opposite the 60
angle so that means it is " A 3" or a
length of 8 3 . Totes Obvi.
5. Oscar’s dog house is shaped like a tent. The slanted sides are both 5 feet long and the bottom of the house
is 6 feet across. What is the height of his dog house, in feet, at its tallest point?
Mr. O’Malley did it two ways as shown below. Which way is correct? Explain.
Mr. O’s Method # 1
Pythagorean Theorem
52  32  x 2
Mr. O’s Method # 2
Altitude To Hypotenuse
x 2  (3)(3)
25  9  x 2
x2  9
x3
16  x 2
4x
So the height is 3 feet.
So the height is 4 feet.
Explanation For The Correct Method
Geometry
Triangle Trampler: _________________________________________ Per: _
Section 9.1 – 9.4 Extra Review
Date: _____________
1. Determine if the following side lengths can create a triangle as well as the type of triangle formed
a) 14, 12, 9
b) 2, 5, 9
c) 8, 10, 6
d) 8, 16, 8
e) 8, 15, 18
2. Find the value of x in the diagram shown
3. Find the perimeter of a rhombus with diagonals of lengths 12 and 16 omalleters respectively.
4. Marianne and Ken both left a riding stable at 10 A.M. Marianne trotted south at 10 kph while Ken
galloped east at 16 kph. To the nearest kilometer, how far apart were they at 11:30 A.M.?
5. How far is it across the quicksand?
6. Find the value of x in all 3 diagrams
7. The altitude of a right triangle divides the hypotenuse into two segments whose lengths are 9 and 3 cm.
Find the lengths of the other two legs and the altitude.
8. Find the values of x and y in all 3 diagrams shown
9. Find the length of a diagonal of a square whose perimeter is 144 cm.
10. Find the perimeter of the trapezoid shown below to the nearest tenth.