40 + 2x - 30 + x + 20 = 180
3x + 30 = 180
3x = 150
x = 50
m<B = 2x - 30
m<B = 2(50) - 30
m<B = 100 - 30
m<B = 70
A) The first step needs 100 bricks, the second needs 98, the third needs 96, and so on. Therefore the number of bricks for the nth step is: a_n = a_1 + d(n-1), where a_1 = 100 (the first term), d = -2 (difference).
a_n = 100 - 2(n-1) = 102 - 2n, and for the 30th step, a_30 = 102 - 2*30 = 42. So the top step will need 42 bricks.
b) The total staircase will need: 100 + 98 + 96 + ... + 44 + 42, and there are n = 30 terms. Using the formula for the sum of an arithmetic sequence:
S = (a_1 + a_n)*n/2 = (100 + 42)*30/2 = 2130
Therefore, 2130 bricks are required to build the entire staircase.
Answer:
Step-by-step explanation:
Surface area is pretty synonymous with area.
How much paint is needed to paint the outside of a birdhouse?
Paint is measured in volume, so not surface area
How much wallpaper is needed to cover the walls of your room?
Since its just the walls its not total surface area, but surface area of the walls.
How much water will it take to fill a rectangular container?
water is measured in volume, especially when wanting to fill something.
How much topsoil can a gardener place in his wheelbarrow?
Wants to know how much topsoil is needed to FILL the wheelbarrow, filling is volume. So not surface area.
How much fabric is needed to make a pillowcase for a pillow?
Not asking to fill the pillowcase, just how much is needed for the thin, one layer thick case. So this is surface area.
<span>4*(5+3)-(8/4)+3*4
4(8) - (2) + 3 x 4
32 - 2 + 12
30 + 12
42
The answer is 42, I believe.</span>
Answer:
the first ones >
Step-by-step explanation:
the second ones <
