Download 2 = 3.14

Classwork 13
APRIL 21, 2013
Area of a circle; Surface areas of cube, cuboid, cylinder.
We derived in class the area a circle
𝑆 = 𝜋𝑟 2
𝐿 = 𝜋𝐷 = 2𝜋𝑟
𝜋 = 3.14
π - is a coefficient, no units.
Cube
Cuboid
Cylinder
Decimal numbers review:
Rounding decimal numbers:
≈is a rounding sign,
the rounding rule is: if next decimal
place is 5 or more, then add 1; if next decimal place 4 or less, - do nothing.
MATH 4: HOMEWORK 13
APRIL 21, 2013
1. Find the side of the largest square….
The figure to the right is
composed of several squares.
The smallest square has side 1
(in some units). What is the side
of the largest square?
2. Find a surface area of:
(for all shapes show your calculations, not just the answer)
a. A cube with a side 5 cm;
b. A cuboid with sides 3cm, 4cm, 5 cm.
c. A cylinder, with radius 2cm, and height 2cm. In your final answer please
leave π, as a letter.
3. Write the following lengths in meters, using decimals (e.g., 3.15 meters): 117 cm;
1
2m 41 cm; 42 m; 5 cm; 30 cm; 30 cm 2 mm
[If you have forgotten: 1m =100 cm, 1 cm=10 mm]
4. Write each of the following lengths in meters and round off to one decimal place:
1
1.57 m; 12 m; 12 m 72 cm; 231 cm; 4 cm
5. Convert to decimal the following fractions:
3
1 13
,2 , ,
4
2 18
6. A teacher asked the students to add two decimal numbers, rounding off the result
to the nearest whole number. One student first rounded off each of these numbers
to the nearest whole number, then added them. The other student first added the
given decimals, and then rounded off the result to the nearest whole number. Is it
possible that they get different results? If so, show how it can happen; if
impossible, explain why.