( a ) |
Express C in terms of x . |
|
( b ) |
Write down the cost of manufacturing a cubical block of side 6 cm . |
|
Suppose that the extra cost $ 12 is taken into account . | ||
( c ) |
Find the length of the side of a cubical block with cost $ 40 . |
|
|
The cost factor r is defined as r
�
|
0.875C. |
|
( d ) |
Express r in terms of x . |
|
( a ) |
C � kx , where k �
0
|
( M1 ) for valid approach |
|
|
35 �
10k k � 3.5 �C�
3.5x
|
A1 |
||
( b ) |
$ 21 |
A1 |
|
( c ) |
40
�3.5x �
12
|
( M1 ) for setting equation |
|
|
28 �
3.5x
|
|||
|
x �
8
|
|||
Thus , the required length is 8 cm . |
A1 |
||
( d ) |
r �
1.75
|
x |
A1 |