Answer: B
<u>Step-by-step explanation:</u>
₁₂C₇ is read as "12 choose 7" which means you are choosing 7 out of 12. Since it is a combination and not a permutation, order does not matter.
Since we're looking for the rate of kilograms per minute, we can represent the rate as
. We just need to divide the kilograms crushed by the time it takes to crush them to obtain R:
Step-by-step explanation:
1. The first step has 1 block. The second step has 2 blocks. The third step has 3 blocks. So the nth step needs n blocks.
2. A staircase with n steps has 1 + 2 + 3 + ... + n steps. This is an arithmetic sequence where the first term is 1 and the last term is n. The sum of the first n terms is:
y = n/2 (1 + n)
3. Solve for n.
2y = n (1 + n)
2y = n² + n
0 = n² + n − 2y
Using quadratic formula:
n = [ -1 ± √(1 − 4(1)(-2y)) ] / 2
n = [ -1 + √(1 + 8y) ] / 2
I don’t why it kinda blurry for me.