1 + 2 + 3 plus 10 equals 55

1 + 2 + 3 plus 10 equals 55

The sum of head and tail equals 11, there are five 11

At present, there are two kinds of wine with 60% and 38% mass fraction. To prepare 440G wine with 45% alcohol, how many grams should be taken from each of the two kinds of wine?

To prepare 45% liquor, the mass ratio of 60% and 38% liquor is (45-38) / (60-45) = 7 / 15
440 × 7 / (7 + 15) = 140 g should be taken from 60 wines
440 × 15 / (7 + 15) = 300 g from 38 liquor

1 / 4 and 4 / 25

1/4=25/100
4/25=16/100
If you don't understand this question, you can ask,

1 × 4 / 1 + 4 × 7 / 1 + 7 × 10 / 1 + 10 × 13 / 1 + 13 × 16 / 1 are calculated by simple method

1 × 4 / 1 + 4 × 7 / 1 + 7 × 10 / 1 + 10 × 13 / 1 + 13 × 16 / 1
=1/3(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)
=1/3(1-1/16)
=1/3x15/16
=5/16

1. What is the width of the silver edge of an 8cm × 12cm photo frame, if the width of the silver edge is the same as that of the photo frame and the area of the silver edge is equal to that of the photo frame?
2. The floor of the conference hall is rectangular, with an area of 224 square meters. The area of the left wall is 126 square meters, and the area of the back wall is 144 square meters. How many meters are the length and width of the conference hall?

Let the width of the silver edge be xcm
（12+2x）X（8+2x）=2x12x8
The solution is x = 2 or x = - 12
2. The director of the conference hall is XM
The height of the wall is 144 / XM, so the width is 126 / (144 / x) M
x（126/（144/x））=224
The solution is x = 16 or x = - 16
The conference hall is 16m long and 14m wide

22 36 40 56 68 how to reason

22
36 =22+12
40=36+14=22+12+14
56=40+16=22+12+14+16
68=56+18=22+12+14+16+18
Namely
+12 +14 +16 +18
22 36 40 56 68

How to solve that x divided by two ninths equals six seventh

Divide or divide

A simple method to calculate 5 / (7 / 13) / (13 / 16) / (16 / 19) / (19 / 21)

5/(7/13)/(13/16)/(16/19)/(19/21)
=5*7/13*13/16*16/19*19/21
=5*7/21
=5*1/3
=5/3

Ax ^ 2-ay ^ 2-bx + by use of group decomposition method to solve fast!

Original = (AX & # 178; - ay & # 178;) - (BX by)
=a(x+y)(x-y)-b(x-y)
=(x-y)(ax+ay-b)

3.5 minus the quotient of 8 divided by 4, the difference is multiplied by 2.5, what's the result?

7.5