Answer:
- number of multiplies is n!
- n=10, 3.6 ms
- n=15, 21.8 min
- n=20, 77.09 yr
- n=25, 4.9×10^8 yr
Step-by-step explanation:
Expansion of a 2×2 determinant requires 2 multiplications. Expansion of an n×n determinant multiplies each of the n elements of a row or column by its (n-1)×(n-1) cofactor determinant. Then the number of multiplies is ...
mpy[n] = n·mp[n-1]
mpy[2] = 2
So, ...
mpy[n] = n! . . . n ≥ 2
__
If each multiplication takes 1 nanosecond, then a 10×10 matrix requires ...
10! × 10^-9 s ≈ 0.0036288 s ≈ 0.004 s . . . for 10×10
Then the larger matrices take ...
n=15, 15! × 10^-9 ≈ 1307.67 s ≈ 21.8 min
n=20, 20! × 10^-9 ≈ 2.4329×10^9 s ≈ 77.09 years
n=25, 25! × 10^-9 ≈ 1.55112×10^16 s ≈ 4.915×10^8 years
_____
For the shorter time periods (less than 100 years), we use 365.25 days per year.
For the longer time periods (more than 400 years), we use 365.2425 days per year.
Haoyu, I'm telling Ms. Mak about your behavior. Expect not to see tomorrow, you were cheating on the math test. I will also contact your parents. Reply to me immidetly if you do not want to get exposed to everyone.
An equation that correctly represent this relationship if x represents the number of pounds of fertilizer and y the number of ounces of weed killer is 0.5x + 3.5y = 70
<u>Solution:</u>
Given that, Bill spent 70 on fertilizer and weed killer for his lawn
Each pound of fertilizer cost 50 cents and each once of weed killer cost 3.50
We have to write an equation, if x represents the number of pounds of fertilizer and y the number of ounces of weed killer.
Now,<em> total amount = amount for fertilizers + amount for weed killers.</em>
Total amount = number of pounds of fertilizers x cost per pound + number of ounces of weed killer x cost per ounce.
Hence, the equation is 0.5x + 3.5y = 70
18 is the answer you're welcome
