S = 3 x 3 / 10 + 3 x 3 / 40 + 3 x 3 / 88 + ... + 3 x 3 / 343

1. Find x, given that:

\(\left(x+\frac{1}{3}\right)+\left(x+\frac{3}{40}\right)+\left(x+\frac{3}{88}\right)=\frac{31}{22}\)

2. The arithmatic average of three numbers is equal to 13.5 . The average of the first number and second number is 13, and the average of the second number and third number is 13.85 . Find the three numbers.

3. Compare A and B, given that:

A = 2.015 x 201.7

B = 20.16 x 20.16

Tính nhanh

G= 2 x 31 x 12 + 4 x 6 x 42 + 8 x 27 x 3  

C = 46 - 45 + 44 -43 + 42 - 41 + .... + 2 -1

I = 7 x 48 x 6 + 21 x 12 x 2 +14 x 40 x 3 

( Giải ra )

TÍNH NHANH

111112222233333 + 888887777777777 =

3456 + 6544 =

10 - 9 + 3 x 12 + 9 - 8 =

12354 x 4 + 88 =

(x + 10) x 3 = 120

x + 10 = 120 : 3

x + 10 = 40

x = 40 - 10

x = 30 

Tính nhanh

a, 9,8 + 8,7 +7,6 + ... + 2,1 -1,2 -2,3 - 3,4 - ... - 8,9

b, 1,18  x 1230 + 0,9 x 4567 x 2 + 3 x 5310 x 0,6 / 1 + 4 + 7 + 10 + ... + 52 + 55 - 514 

c, 0,36 x 950 + 0,18 x 726 x 2 + 3 x 324 x 0,12 / 1 + 3 + 5 + ... + 29 + 31 -152

Tính nhanh:

12 x 23 + 23 x 88 / 46 x 3 + 46 x 14

3. Tính bằng cách thuận tiện

a, 45,28 + 51,17 - 15,28 - 12,17

b, ( 72,69 + 18,47 ) - ( 8,74 + 22, 69 )

c, 4,86 x 0,25 x 40

d, ( 42,8 x 6,9 - 6,9 x 8,3 ) : 34,5