An old man said, my age plus 17 is divided by 4, and then minus 15 is multiplied by 10. It happens to be 100 years old. How old is this old man?

An old man said, my age plus 17 is divided by 4, and then minus 15 is multiplied by 10. It happens to be 100 years old. How old is this old man?

Suppose the old man is x years old
[(x+17)/4-15]*10=100
(x+17)/4-15=100/10=10
(x+17)/4=25
x+17=100
x=83
The old man is 83 years old

3 times 5 numerator 1 plus 5 times 1 in 7 plus 7 times 1 in 9 plus 9 times 1 in 11. Plus 2007 times 1 in 2009

If you think about it, it's a summation. 3 / 5 is greater than 1 / 3. How can the answer be less than 3 / 5
3/5+5/7+.+2007/2009=?
The general term formula sum ((2 * n-1) / (2 * n + 1), (n = 2.. 999);
1*3+3*5+5*7+.+(2n-1)(2n+1)
=(4*1^2-1)+(4*2^2-1)+(4*3^2-1)+.+(4n^2-1)
=4(1^2+2^2+3^2+.+n^2)-(1+1+1+.+1)
=4*n(n+1)(2n+1)/6-n
=n(4n^2+6n-1)/3
The square sum formula of the first n natural numbers: 1 ^ 2 + 2 ^ 2 + 3 ^ 2 +. + n ^ 2 = n (n + 1) (2n + 1) / 6
When n = 1003, I get it. Then I subtract 1 / 3 to get the answer

There is an old man. He adds 16 to his age this year, removes it by 5, subtracts 10, and finally multiplies it by 10. He is exactly 100 years old. How old is the old man this year?

[(x+16)/5-10]*10=100
(x+16)/5-10=10
(x+16)/5=20
x+16=100
x=84

(1/3*5+1/5*7+.+1/1997*1999

1/(2n+1)(2n+3)=1/2[1/(2n+1) - 1/(2n+3)]
1/3*5+1/5*7+.+1/1997*1999
=1/2（1/3-1/5+1/5-1/7+…… 1/1997-1/1999）
=1/2（1/3-1/1999）
=998/5997

An old man said, "add 17 to my age and divide it by 4. Subtract 15 and multiply it by 10. It's exactly 100 years old." how old is the old man this year? "

Let the age of the elderly be X
［（x+17）/4 -15］10=100
（x+17）/4-15=10
（x+17）/4=25
x+17=100
x=83

(-421)×(-1/4)-0.25×(-7 1/2)-28.5×25%

(-421)×(-1/4)-0.25×(-7 1/2)-28.5×25%
=421x0.25+7.5x0.25-28.5x0.25
=(421+7.5-28.5)x0.25
=400x0.25
=100

An old man said, "add 12 to my age, divide by 4, subtract 12, and multiply by 10. It's exactly 100 years old." how old is the old man now?

(100 △ 10 + 12) × 4-12, = 22 × 4-12, = 88-12, = 76 (years old). A: This grandfather is 76 years old now

When 40 students do three math problems, 25 students do the first problem right, 28 students do the second problem right, and 31 students do the third problem right, so at least there is one______ I got three questions right

40 - (40-25) - (40-28) - (40-31) = 40-15-12-9, = 4 (people). A: at least 4 people have done three questions correctly

How old is this grandfather now? Add my age to 5. Divide by 4, then subtract 12. Multiply by 10, it's exactly 100 years old

（100÷10＋12）×4－5

The first of several mathematics problems in the second semester of Grade Seven: 0.25 ^ 2007 times 4 ^ 2008 minus 8 ^ 100 times the power of 300
Second: let 3 ^ n + m be divisible by 10, and it is proved that 3 ^ n + 4 + M can also be divisible by 10

1
0.25^2007*4^2008-8^100*(1/2)^300
=(1/4)^2007*4^2007*4-2^(3*100)/2^300
=4-1
=3
two
3^n+4+m
You must have forgotten to add parentheses