A and B practice running on the circular track. A runs one circle in one minute on average, B runs one circle in 1.2 minutes on average. If they run in the same direction at the same time, how many minutes will it take for them to meet for the first time?

Let's meet in X minutes
Lie equation: X / 1-x / 1.2 = 1
1.2x-x=1.2
0.2x=1.2
x=6
A: six minutes for the first time
(I'm a freshman in junior high school. It's a bit difficult. Please choose me and beg.)

In △ ABC, ab = AC, ∠ BAC = 120 °, points D and F are the midpoint of AB and AC respectively, ed ⊥ AB and GF ⊥ AC. if BC = 15cm, calculate the length of eg

As shown in the figure, connecting AE and Ag, ∵ D is the midpoint of AB, ed ⊥ AB, ∵ EB = EA, ∵ Abe is an isosceles triangle, and ∵ B = 180 °− 120 ° 2 = 30 °, and ∵ BAE = 30 °, and ∵ AEG = 60 °. The same principle can be proved: ∵ age = 60 °, and ∵ AEG is an equilateral triangle, ∵ AE = eg = AG, and ∵ AE = be, Ag = GC, ∵

(1.992 + 19.92 + 199.2) / 0.111 simple calculation

(1.992+19.92+199.2)/0.111
=(1.992+1.992*10+1.992*100)/0.111
=1.992*（1+10+100)/0.111
=1.992*111/0.111
=1992*（0.111/0.111 ）
=1992

The perimeter of a right triangle is 120cm, the longest side is 50cm, and the ratio of the two right sides is 3:4. What is the area of the triangle?

Sum of two right angle sides: 120-50 = 70 cm
The length of one right angle side is 70 × 3 / (3 + 4) = 30 cm
The other right angle side length is: 70-30 = 40 cm
Area = 1 / 2 × 30 × 40 = 600 square centimeter

37 * 52 = 1924, then 19.24 = {} * {} write four groups

19.24=3.7*5.2
=0.37*52
=37*0.52
=370*0.052

In the triangle ABC, if AC equals 13, BC equals 15 and CD equals 12, then its area is?

Helen Qin jiuzhao formula
S=√p(p-a)(p-b)(p-c) p=(a+b+c)/2
S=√20*7*5*8=20√14

How to solve the equation for molecule 15 with 5x = 19

5x=15/19
Both sides of the equation are multiplied by 19 to obtain:
95x=15
The coefficient is 1
x=3/19

The volume of a cone is 9dm and 179, the height is 18dm and its bottom area is () DM and 178;

The volume of a cone is 9dm & # 179, the height is 18dm, and its bottom area is (1.5) DM & # 178;

In the series of - 49, - 48, - 47,. 100, (1) what is the sum of the first 99 numbers? (2) what is the sum of the first 100 numbers?

（1）
-49+99-1 = 49
So these numbers go from - 49 to 49, paired in pairs:
Sum = (- 49 + 49) + (- 48 + 48) + +(-1+1)+0 = 0
(2)
The first 100 numbers are - 49 to 50
Sum = (- 49 + 49) + (- 48 + 48) + +(-1+1)+0 + 50 = 50

It is known that: as shown in the figure, the two heights BD and CE of acute angle △ ABC intersect at point O, and ob = OC. (1) prove that △ ABC is an isosceles triangle; (2) judge whether point O is on the angle bisector of ∠ BAC, and explain the reason

(1) It is proved that: ∵ ob = OC, ∵ OBC = ∵ OCB, ∵ acute angle △ ABC two high BD and CE intersect at O, ∵ BEC = ∵ CDB = 90 °, ∵ BEC + ∵ BCE + ∵ ABC = ∵ CDB + ∵ DBC + ∵ ACB = 180 °, ∵ - BEC - ∵ BCE = 180 ° - CDB - ? CBD, ? ABC = ? ACB, ∵ AB = AC, ? ABC is isosceles triangle; (2) Reason: connect AO and extend BC to F. in △ AOB and △ AOC, ab = acob = ocoa = OA ≌ AOB ≌ AOC (SSS). ≌ BAF = ≌ CAF, ≌ point O is on the angular bisector of ∠ bac

A and B practice running on the circular track. A runs one circle in one minute on average, B runs one circle in 1.2 minutes on average. If they run in the same direction at the same time, how many minutes will it take for them to meet for the first time?