Download Mathematics 3

Mathematics 3.
March 13, 2011
Class work .
#1.
The long multiplication of the numbers, which end with zeros, is written
in this form:
310
x 3
930
26
x 20
520
28
x 30
490
x 2_
36
x 20
#2.
Compute:
30 x 50 =
70 x 90 =
8 x 300 =
600 x 5 =
800 x 80 =
3 x 7000 =
60 x 400 =
200 x 900 =
#3.
a
There are liters of juice in 5 identical
cans. How many liters of juice are there
in 12 cans?
a
There are liters of juice in 5 cans.
How many cans of this type do we need
to distribute 12 liters of juice?
c
One bag holds kg of barley, and
another bag holds three times as many
kilograms as the first bag. How many
more kilograms are here are in the
second bag than in the first?
m kg of potatoes, 20
kg per box, and n kg of carrots, 30 kg
A truck delivered
per box. How many boxes of vegetables
did the truck deliver in all?
160
x 6_
25
x 40
#4
a) Annie was going to New York City. On her way she met 3 men. Each man had a bag.
There were 3 cats in each bag. How many living beings were traveling to New York
City
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b) The length of a wooden log is 5 feet. Every minute we cut 1 foot of wood off. How
many minutes will it take to cut the whole log?
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c) A man met a family of grandfather, father and son. The man asked how old they were.
The grandfather answered: “We are 100 years old in all.” Then the man asked the
father the same question. The father said: “Altogether my son and I are 45 years old.
My son is 25 years younger than me.” The curious man was no able to find out the age
of these grandfather, father, and son. Can you help him?
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Division by 10, 100, 1000…
#5
Find the result using example on the picture below:
Division is an operation, which is opposite to multiplication. When we divide
by 10, 100, 1000 and so on, the only thing we need to do is to get rid of a zero,
2 zeroes, 3 zeroes and so on at the right end of the number.
#5 Compute:
5600  10 
290000  100 
8400  100 
60000  10 
42000  1000 
170000  1000 
75000  100 
9800000  10000 
250  10 
550  10 
3000  100 
4400  100 
35000  1000 
33000  1000 
400000  10000 
220000  10000 
#7
Compute. There is something special about these examples. What do you
notice? Which example can we write next?
9 x90
800 x 8
70 x 700
6 x 60000
#9
Use long multiplication to compute:
6900 x 8
790 x 600
6300 x 40
92 x 52
5400 x 70
39000 x 60
#11
.
#12
∠ABC is the complement or supplement of ∠CBD
#13
Triangles:
How do we call a figure shown on the picture above?
The figure is called a triangle, because it has 3 angles. The
segments, which construct a triangle, are called the sides of a
triangle. The sum of the sides of a triangle is called a
perimeter (the sum of the segments AB + BC + CA).
Usually one of the sides of a triangle is drawn horizontally.
Examine the triangles on the picture below. What is the difference between the triangles
on the picture?
One of the angles in
△A1B1C1 is a right angle. A
triangle with a right angle is
called a right triangle.
How do we call a △A2B2C2?
Obtuse. Why?
Can a triangle have two obtuse angles? Why or why not?
Can a triangle have two right angles? Why or why not? What happens to the sides of two
right angles if we extend them?
Compare the sides and the angles of a △ABC. Which side is the longest? Which angle is
the largest? Which side is the shortest? Which angle is the smallest?
Conclusion: In a triangle, the largest angle lies opposite the longest side. In a triangle the
smallest angle lies opposite a shortest side. Also the opposite is true: the shortest side is
across the smallest angle.
What can you say about the sides of a △ABC and its
sides?
A triangle, which has three congruent sides, is called an
equilateral triangle, or a regular triangle.
What can you tell about the sides AC and AB in a △ABC? Angles ABC and ACB?
A triangle, which has 2 congruent sides is called isosceles triangle.
Does any isosceles triangle have two congruent angles? Do you agree?
Think! If the angles were not congruent then one of the angles would be greater than the
other. For example angle ABC would be greater than angle ACB. In a case like this would
the sides AB and AC be congruent?
#14.
How do we call the triangles on the pictures below?
#15 Using a blue pencil, mark the figure, which is formed by intersection of:
a) △ABC and △ACD
b) △ABC and △ABD
#16 Ordered pairs.