East China Normal University Edition Fifth Grade Mathematics (Enhanced Edition) Lesson One Exercise

Question 1: The volume is the sum of the volumes of all small cubes. 1x1x1x (1+4+9+16) = 30 cubic centimeters.

The surface area is the sum of all exposed surfaces, and the front and back, up and down, left and right areas are equal respectively.

Front and rear area:1x1x10x2 = 20cm2.

Left and right areas:1x1x10x2 = 20cm2.

Upper and lower areas:1x1x16x2 = 32cm2.

Surface area: 20+20+32=72 cm2.

Question 2: (1) trapezoidal area: (6+12) x9x1/2 = 81cm2.

(2) Because the area of triangle ADE is equal to the area of triangle CDF, let CF be x cm long.

9x* 1/2=6*6* 1/2

Solution: x=4

That is, CF is 4 cm long.

(3) BF = BC-CF = 12-4 = 8cm。

Trapezoidal ADFB area: (6+8) x9x 1/2 = 63cm2.

Triangle ADE area: 6x6x 1/2 = 18cm2.

BEF area of triangle: be = 9-6 = 3cm.

3x8x 1/2= 12 cm2

DEF area of triangle: 63- 18- 12 = 33cm2.