The black-and-white beads are white and black, forming an equilateral triangle. When the difference between the number of black-and-white beads in the equilateral triangle is 30, how many should be arranged on each side of the triangle?

Two rows: White 1, black 2, poor 1
Third row: white 4, black 2, poor 2
Four rows: white 4, black 6, poor 2
Five rows: white 9, black 6, poor 3
Six rows: white 9, Black 12, poor 3
Seven rows: white 16, Black 12, poor 4
Eight rows: white 16, black 20, poor 4
.
.
.
30*2=60
There should be 59 or 60 rows on each side

A cuboid glass tank with a floor area of 96 square meters and a height of 10 cm contains 5 cm of water. Put an iron bead into it, and the water surface rises by 2 cm. Q1: what is the volume of the iron bead? Q2: at least a few such beads should be put before the water will overflow the glass tank?

It's 96 square centimeters, right?!
The volume of iron bead is 96 × 2 = 192 (CM & sup3;)
960 △ 192 = 5 at least 5

A measuring cylinder containing 300 ml of water. After putting three steel balls with equal radius, the water surface rises to 360 ml. the volume of each steel ball is______ Cubic centimeter

(360-300) △ 3, = 60 △ 3, = 20 (ML), 20 ml = 20 cubic centimeter; answer: the volume of each steel ball is 20 cubic centimeter

There are five red balls, five white balls and two black balls in total. They are arranged in the order of five red balls, five white balls and two black balls?

(red 5 + White 5 + Black 2) * 167 = 2004
The fifth is red
So white is 167 * 5 = 835

There are the same number of red balls and white balls in the box. Six red balls and four white balls are taken out each time. After taking them several times, the red balls are just finished and there are still 10 white balls left. How many times have you taken them? How many red balls are there in the box?

10 △ (6-4), = 10 △ 2, = 5 (Times); 6 × 5 = 30 (Times); a: a total of 5 times; there are 30 red balls in the box

Find the rule: black and white black and white black and white. Q: how many white ones are there in the first 2009?
Now it will. Don't answer!

The number of words ending with "white" is: 2, 3, 4, 5,
So an = n + 1, Sn = (n + 3) n / 2
Let Sn = 2009
N = 61.9, rounded to 61, each item has only one "white" at the end,
therefore
In the top 2009, there are 61 white

There is a pile of chessmen, arranged in the order shown in the figure below, then the 42nd is () black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black black

White. Use six units. 42 / 6 = 7. The last one in line 7 is white

There is a pile of black and white chessmen, in which the number of black chessmen is twice that of white chessmen. If four black chessmen and three white chessmen are taken out of the pile at the same time, then after several times, there is one white chessman left and 18 white chessmen left?

(18-2) / (3 × 2-4), = 16 ^ (6-4), = 16 ^ 2, = 8 (Times). Answer: after 8 times, there is only one white and 18 black

There is a box of black and white chess pieces, and the number of black pieces is twice that of white pieces. If you take 4 black pieces and 3 white pieces each time, after the white pieces are taken, there are 16 black pieces left. Ask the black and white chess pieces
I'm a fourth grade student. Do you have a calculation method without equation?

Originally, if you take 6 sunspots and 3 white pieces each time, the two pieces will be finished
Now only 4 sunspots are taken, less than 6, so there is a surplus of sunspots
Each time, there are two sunspots left
So as long as we know how many times two sunspots are left, we will know how many times we have taken them
yes
16 / (3 x 2 - 4) = 8 times
Sunspots 4 x 8 + 16 = 48
Baizi 3 x 8 = 24

There is a pile of black and white pieces, the number of black pieces is twice that of white pieces
There is a pile of black and white chessmen. The number of black chessmen is twice that of white chessmen. If five black chessmen and four white chessmen are taken out each time, after several times, the white chessmen are gone, and there are still 24 black chessmen. How many chessmen are there in this pile?
Find two solutions? One is to list equations, the other is not to list equations!

Let's take x times
5 x + 24 = 4 x * 2
x = 8
8 * 5 + 24 = 64 sunspots
8 * 4 = 32 white

The black-and-white beads are white and black, forming an equilateral triangle. When the difference between the number of black-and-white beads in the equilateral triangle is 30, how many should be arranged on each side of the triangle?