This is the number of combinations of 4 from 12
12C4 = 12!
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4! 8!
= 12*11*10*9 11*5*9 = 495
-------------- =
4*3*2*1
I hate rounding.
Let's call the diagonal x. It's the hypotenuse of the right triangle whose legs are the rectangle sides.
According to the problem we have a length x-4 and a width x-5 and an area
82 = (x-4)(x-5)
82 = x^2 - 9x + 20
0 = x^2 - 9x - 62
That one doesn't seem to factor so we go to the quadratic formula

Only the positive value makes any sense for this problem, so we conclude

That's the exact answer. Did I mention I hate rounding? That's about
x = 13.6 meters
Answer: 13.6
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It's not clear to me this problem is consistent. By the Pythagorean Theorem the diagonal satisfies

which works out to

That's not consistent with the first answer; this problem really has no solution. Tell your teacher to get better material.
Answer:
2,438
Step-by-step explanation:
53
46
______
318
212
_______
2438
6 times 3 is 18. Put the 8 in the ones place and carry the 1 ~ 6 times 5 is 30. Add the carried 1 and you have 31. Put that next to the 8. ~ 4 times 3 is 12. put the 2 under the 1 in 318 and carry the 1. ~ 4 times 5 is 20. Add the carried 1 and you have 21. ~ Put that next to the 2. Now add 318 to 2120 and you have the answer of 12438.
What? That doesn't make sence! Any way if you mean 1997 to 2014 how many years.
1,680 divided by 400 = 4.2
So we know that Xian has done 4.2 laps.
4.2 divided by 14 = 0.3
0.3 x 100 = 30%
Therefore, Xian has finished 30% of the run