Answer:
Its C
Step-by-step explanation:
Just took the test and found out it's not infact 5, but it's 25
If he put 10 in the bowl and there are 150 cards, the chance for him to win would be 10/150.
now by simplifying it, you get 1/15.
therefore answer is C
Answer:
80 sqcm
Step-by-step explanation:
area of the full rectangle is 96 sqcm (12x8) and then you subtract the area of the cutout (4x4)
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.
