Aunt Li went to the market to buy fruits. She spent 18.6 yuan on apples and 4.6 yuan on bananas. How much did Aunt Li spend on fruits?

Aunt Li went to the market to buy fruits. She spent 18.6 yuan on apples and 4.6 yuan on bananas. How much did Aunt Li spend on fruits?

Banana spent: 3.5 * 4.6 = 16.1 yuan
A total of 18.6 + 16.1 = 34.7 yuan

Aunt Li spent 24.7 yuan on 3 kg apples and 5 kg pears, 2.9 yuan per kg apples, how much yuan per kg pears?

(24.7-3 * 2.9) / 5 = 3.2 yuan

Arrange all positive integers into a triangular matrix
one
3 5
7 9 11
13 15 17 19
……
According to the above arrangement, the first number from left to right in line n (n > = 3) is?

The first number from left to right in line n (n > = 3),
That is, the first [1 + 2 + 3 +] from 1 +(n-1)] + 1 odd numbers
In addition, the odd number a starting from 1 can be expressed as 2a-1
So the result is: 2 × [1 + 2 + 3 + +(n-1)]+2-1=n(n-1)+1

X ^ TBX = x ^ tax + x ^ 2 prove that the determinant of B is greater than that of A

With the method of definition, it is proved that x ^ TBX is always greater than zero when x is not zero

5.4 multiplication formula (1)
Using square difference formula to calculate
（1）2006×2008-2007²
(2) (x + y) (2x-y) - (x + 2Y) (x-2y) where x = 3, y = 4 (simplified recalculation)

(1)(2007-1)(2007+1)-2007²
=2007²-1- 2007²
=-1
(2) The original formula = 2x & sup2; + xy-y & sup2; - X & sup2; + Y & sup2;
=x²+xy
Substituting x = 3, y = 4
Then the original formula = 9 + 12 = 21

The first line is 1, the second line from left to right is 2,3, the third line is 4,5,6, and the fourth line is 7,8,9,10
How many years is the last number on line 50? Why?

So the total number of 50 rows is (1 + 50) * 50 / 2 = 1275. The first row 1, the second row from left to right are: 2,3, the third row: 4,5,6, the fourth row: 7,8,9,10. The size of the last number in the pyramid number column is actually

What are the multiples of 6 within 100

6,12,18,24,30,36,42,48,54,60,66,72,78,84,90,96

The first practical problem of exercise 6.11 in mathematics exercise book of grade 6
Xiao Li took a 10 yuan note to the bus station and got 13 dimes and 1 yuan coins. How many of the two coins are there?
It's best to use x, y

Suppose there are x 50 cents and Y 1 yuan coins. 50 cents = 0.5 yuan
X+Y=13 ⑴
0.5X+Y=10 ⑵
(2) formula: y = 10-0.5x (3)
Substituting formula (3) into formula (1),
X = 6 pieces
Substituting x = 6 into formula (1)
Y = 7 pieces

There are 10 red, yellow, blue and white balls each, mixed in a cassette, and at least one touch out______ In order to ensure that there are two balls of the same color

4 + 1 = 5; answer: at least 5 at a time, to ensure that there are 2 balls of the same color; so the answer is: 5

If the square of (x + 1) is equal to 2, then X=

X + 1 = ± root 2
X = - 1 - radical 2, x = - 1 + radical 2