6th Grade Math Textbook, Fundamentals

Round each dimension up to the nearest whole number.

length of each rectangular face22.3 in. 23 in.

base of the right triangular base11.8 in. 12 in.

height of the right triangular base13.2 in. 14 in.

side parallel to the hypotenuse of the triangular base18.7 in. 19 in.

Estimate the area of the triangular base.

A bh

A (12)(14)

 (168) 84 in.^2

Estimate the area of each lateral face.

Aw

A 1 (12)(23) 276 in.^2

A 2 (19)(23) 437 in.^2

A 3 (14)(23) 322 in.^2

Estimate the total surface area.

S 2 BA 1 A 2 A 3

S2(84)  276  437  322

1203 in.^2

Rename square inches as square feet.

Divide: 1203  144 8.35

1203 in.^2 8 ft^2

So Inga needs about 8 square feet of wrapping paper to cover the box.

1

2

1

2

1

2

 &KDSWHU

11-6

Estimate Surface Area

Objective To estimate the surface area of prisms and cylinders

Inga is wrapping a very large present packed in a box
like the one shown. Her measurements, made to the
nearest quarter inch, are shown in the drawing. About
how many square feet of wrapping paper are needed
to wrap the gift?

When computing surface area, sometimes an estimate is sufficient

and an exact calculation is not needed.

There are different types of estimates. An is an estimate

greater than the actual value. It is found by rounding a number up to

a greaternumber. An is an estimate less than the actual

value. It is found by rounding a number down to a lessernumber.

Inga should overestimateto be sure she has enough wrapping paper.

To find about how many square feet of wrapping paper Inga needs,

round each measurement to the nearest whole number. Then compute.

underestimate

overestimate

13.2 in.

11.8 in.

22.3 in.

18.7 in.

Remember:

1 ft 12 in. and 1 ft^2 12 in. 12 in.

or 144 in.^2