I know the answers but I hate simplifying
40) 9y-12
42) -3x+3y-5
If the whole diameter of sphere is 6 inch(means radius is 3 inch) & thickness of material is 1 inch, so the radius of the hollow part should be 2 inch (3-1=2)
The total volume of the ball will be;
= Total volume - Volume of hollow part
= 4/3πr³ - 4/3πr³
= 4/3 × 3.14 × (3)³ - 4/3×3.14×(2)³
= 4 × 3.14 × 9 - 4/3 × 3.14 × 8
= 113.04 - 33.52
= 79.52
If the density of the material is 3.25 g/in3, then the density of 79.52 inch³ should be;
= 79.52 × 3.25
= 258.44 g
Now, if there are 8 spheres in one box, the weight if box will be;
= 258.44 × 8
= 2,067.52 g
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Ahh! Finally done with this, if you have any doubt just do ask me :)
Answer: the cost per unit of gas is $0.28
Step-by-step explanation:
Let x represent the cost per unit of electricity.
Let y represent the cost per unit of gas.
During one month, a homeowner used 500 units of electricity and 100 units of gas for a total cost of $333. This is expressed as
500x + 100y = 333 - - - -- - -- - -- -1
The next month, 400 units of electricity and 150 units of gas were used for a total cost of $286. This is expressed as
400x + 150y = 286 - - - - - - - - - --2
Multiplying equation 1 by 400 and equation 2 by 500, it becomes
200000x + 40000y = 133200
200000x + 75000y = 143000
Subtracting, it becomes
- 35000y = - 9800
y = - 9800/- 35000
y = 0.28
Substituting y = 0.28 into equation 2, it becomes
400x + 150 × 0.28 = 286
400x = 286 - 42 = 244
x = 244/400 = 0.61
