Clever calculation: (1988 + 1986 + 1984 +...) +4+2)-(1+3+…… +1985+1987)

(1988+1986+1984+…… +4+2)-(1+3+…… +1985+1987)
=(2-1) + (4-3) + (6-5) +. + (1986-1985) + (1988-1987) a total of 1988 / 2 = 994 groups
=1+1+1+1+.+1
=1*994
=994
I don't understand

RELATED INFORMATIONS

1. Write 1,2,3,4,5,6,7,8,9,10,11,12 to the 1999 digit in turn to form the 1999 digit. What is the remainder of this number divided by 9?
2. 956 divided by 4 minus 238 times 358 minus 258 equals 100, how to make the formula hold You can only add small outline numbers Is 956% 4-238 * 358-258 = 100
3. "An integer divided by 1 / 5 is five times larger
4. How to spend money indiscriminately Spending money indiscriminately and accumulating experience for going to the society in the future
5. How much is seven and two fifths minus one and two thirds
6. Simple calculation 17 * (2 / 19-1 / 17) * 19 Simple calculation 17 * (2 / 19-1 / 17) * 19
7. Given a number of 10, if it is multiplied by 25, then divided by 2, then multiplied by 3.14, then multiplied by 2, then divided by 3.14! What is the final number?
8. 15 + [] = 51 - [] requires the same number in brackets of the same formula
9. The reciprocal of a number divided by 16 is ()
10. A few + 8 / 9 + 7 / 12 = 2
11. 6.75−2.75÷[10%×(9.75−414)]．
12. What is the mantissa of the product of 18 * 28 *. * 98 * 108
13. 375 × 8 / 9 And 3.5 × 4 / 7, 18 × 2 and 1 / 9, 2 and 9 / 10 + 0.1 × 25-1 and 2 / 9
14. Simple calculation of 72 * 28 + 72 * 72
15. How many centimeters is three fifths of a meter
16. 8 + (- 5) times (- 8) times (- 3 / 4) Multiplication of rational numbers in the first year of junior high school
17. 1 / x + 1-x + 3 / x ^ 2-1 divided by x ^ 2 + 4x + 3 / x ^ 2-2x + 1, where x = - 1 / 2
18. The known number 40 corresponds to 3.0 The number 42.1 corresponds to X The number 45 corresponds to 1.5 How much is x by interpolation, My friend on the first floor, the formula you gave is wrong, 2.25 - (42.5-42.1) × 5 = 2.05.
19. How to use interpolation method to calculate interest rate Given the coefficient of present value (or final value) of annuity and the number of periods n, it is a little unclear when calculating the interest rate according to the interpolation formula Example: a company borrows 20000 yuan at the beginning of the first year, and repays 4000 yuan at the end of each year, which is paid off for nine consecutive years? （P/A,i,9)=P/A=20000/4000=5 When I = 12%, (P / A, 12%, 9) = 5.3282; I = 14%, (P / A, 14%, 9) = 4.9464 So I = 12% + (5.3282-5) / 5.3282-4.9464) * (14% - 12%) = 13.72% The formula I = I1 + (b-b1) / (b2-b1) * (i2-i1), why not I = 12% + (5-5.3282) / 4.9464-5.3282) * (12% - 14%) How to define I1 and I2 in the formula? Which of the 12% and 14% in the above example is I1 and which is I2?
20. How to calculate by interpolation The depth of K0 + 260 is 0.514, the depth of K0 + 280 is 0.472, and the depth of K0 + 262.276 is calculated by interpolation