December 6, 2012 Notes

Surface Area

       - Area is the number of the square units it takes to cover a surface. Always expressed as squared units.

Formulas for finding the area of a square, rectangle, triangle, and circle.

Finding the perimeter of a given area of a circle. 

    Question: A square has an area of 35 squared centimentres. What is the measure of its perimeter.

Find the area of the given shape.

First way: Finding the area of the whole shape including the missing shape.. Then subtract the area of the missing shape from the whole shape to get the area of the given shape.

Second Way: 

Test Question #9 Answers

Question: Close to the surface of the moon, the time a dropped object takes to fall to the surface can be calculated using the formula t= the square root of h/0.81. The time, t, is in seconds and the height, h, is in metres. If an object is dropped from a height of 250 m, how long does it take to reach the surface of the moon? Express your answer to the nearest tenth of a second. 

Math Test, Question # 1

Question:
A car uses fuel at a rate of 10.2 L/ 100 km while travelling at 90 km/h. At this rate of fuel consumption, how many litres of fuel would the car use if it travels 480 km? Express your answer to the nearest tenth of a litre.

This is how I solved this question:

My simple sentence answer:
The car will use 49.0 L of fuel if it travels 480 km.

Textbook Pg. 81 #31

Question: The area of a triangle can be determined using Heron's formula, which requires the side lengths of a triangle. Heron's formula is 

In the formula A is the area; a, b, and c are the side lengths; and s is half the perimeter or a+b+c/2. Determine the area of each triangle with the following side lengths. Express each area to the nearest tenth of a square centimetre. 

a) 15 cm, 12 cm, 10 cmb) 9.3 cm, 11.4 cm, 7.5 cm

The area of the triangle is 59.8 square cm.

b) 9.3 cm, 11.4 cm, 7.5 cm

The area of the triangle is 34.7 square cm. 

Rational Number Word Problems Test, Question 2 by Jay Jay

2. In a cold storage chamber, the temperature drops 5.2C every 10 minutes. If the temperature is initially 19C, what is the temperature in the chamber after 1½ hours?

Important things we know : 

5.2°C down every 10 minutes. (x9 = 90 minutes)

1½ hours  90 Minutes (90 ÷ 10 = 9)

Temperature is 19°C

19°C - (5.2°C x 9)    = 19°C - 46.8°C

                                  = -27.8°C

Therefore, the temperature in the cold storage chamber after 1½ hours is, -27.8°C

Math Test:Answering #4

4.The figure below is composed of seven congruent squares. The area is 43.75cm2. Calculate its perimeter.

A=Area
P=Perimeter

What We Know:
A=43.75cm2
7 congruent squares
P=14 congruent segments

Answer:
43.75cm2/7 =A of ONE square
                    =6.25cm2

square root of 6.25cm2=ONE side of small square
                                     =2.5cm

2.5cmx14=A of shape
                =35cm

Perimeter of the shape is 35cm.

Test Answer #7