Page 34 - 新思维数学学生用书8 样章

2.1 Constructing expressions

12 The shortest side of a triangle is y cm. Tip
The second side is 3 cm longer than the shortest side.
The third side is twice as long as the second side. Start by writing
Write an expression, in its simplest form, for the perimeter expressions for
of the triangle. the second and

13 The price of one bag of cement is $c. third sides.
The price of one bag of gravel is $g.
The price of one bag of sand is $s.
Write an expression for the total cost of

a one bag of cement and three bags of sand
b three bags of cement, four bags of gravel and six bags of sand.
14 The price of one kilogram of apples is $a.
The price of one kilogram of bananas is $b.
The price of one kilogram of carrots is $c.

Write an expression for the total cost of
a one kilogram of apples and half a kilogram of bananas
b two kilograms of bananas and three-quarters of a kilogram of carrots

c three kilograms of apples, a quarter of a kilogram of bananas
and four-fifths of a kilogram of carrots.
15 Brad thinks of a number, y.
Choose the correct expression from the cloud for  5y   y 

when Brad 6   6 + 2   6   2 + 5  
a adds 5 to one-half of y, then multiplies by 6  2y   y 
b adds 6 to one-fifth of y, then multiplies by 2 6   5 + 5   2   5 + 6  
c adds 2 to five-sixths of y, then multiplies by 6

d adds 5 to two-fifths of y, then multiplies by 6.

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