The school held a rope skipping competition. Xiao Hong and Xiao Li jumped 306 times in total. The number of Xiao Hong's jumps was five times that of Xiao Li. How many times earlier were Xiao Hong and Xiao Li

The school held a rope skipping competition. Xiao Hong and Xiao Li jumped 306 times in total. The number of Xiao Hong's jumps was five times that of Xiao Li. How many times earlier were Xiao Hong and Xiao Li

306/（5+1）=51 51*5=255

Xiao Fang's skipping rope is 1.2 meters long, Xiao Ying's is 1.5 meters long, Xiao Xin's is 2.8 meters long, and Xiao Li's is 1.7 meters long. How many ways can you use three of them to form a triangle?

Two, from the axiom of the shortest line segment between two points, we can get the triangle trilateral relationship: the sum of the lengths of any two sides is greater than the third side, and the difference of the lengths of any two sides is less than the third side. So the answer is 2.8, 1.5, 1.7. Or 1.5, 1.7, 2.8

1. Xiao Li, Xiao Hong and Xiao Fang went on a spring outing. Xiao Li bought four loaves and Xiao Hong bought five loaves. After the three people ate them on average, Xiao Fang paid 2.7 yuan. Should Xiao Hong take them back?
2. Only two pancakes can be put in one pan at a time. It takes two minutes to bake one pancake (one on the front and the other on the back) and at least several minutes to bake three pancakes?
3. How many programs can the school choose from three sketches and one from two dance programs?

1. Each person ate 3 pieces of bread, 3 pieces of bread cost 2.7 yuan, so one is 2.7 / 3 = 0.9 yuan. Xiaohong bought 5-3 = 2 pieces for Xiaofang, so she should take back 2 * 0.9 = 1.8 yuan. 2. It takes at least 3 minutes to bake 3 pieces of bread. Put two pieces for the first time, take out one piece after one side is cooked, and put the third piece in. At this time, it takes 1 minute, another minute, and one piece is baked well

In the triangle ABC, angle c is a right angle, BC = AC, BD is the bisector of angle ABC, AE is vertical to BD, the perpendicular foot is e, and BD = 2ae

Extend the extension line of AE BC to F
∵ be is the angular bisector of ∠ CBA, AE ⊥ be
Ψ Δ ABF is an isosceles triangle and E is the midpoint of AF
∵∠BCA = 90°,BE⊥AE,∠BDC = ∠ADE
∴∠CBD = ∠EAD
∵BC = AC
∴△BCD≌△ACF
∴BD = AF
∵AE = AF/2
∴AE = BD/2
∴BD = 2AE

I is the intersection of the three bisectors of △ ABC, and Ca + AI = BC. If ∠ BAC = 80 °, find the size of ∠ ABC and ∠ AIB

Let ID ⊥ AC in D, ie ⊥ BC in E, if ⊥ AB in F, ≁ I be the inner triangle, ≁ ad = AF, CD = CE, be = BF, AC + AI = AD + CD + AI = AF + CE + AI = BC = CE + be, ≁ AF + AI = BF, take point o on BF, make fo = AF, △ AFI ≌ ofI, ≌ IAF = ≌ IOF, AI = IO, and ≁ BF = of + ob, ≌ a

As mentioned above, I is the intersection of the bisectors of three angles of triangle ABC, and Ca + AI = BC. If the angle BAC = 80 degrees, what are the degrees of angle ABC and angle AIB?

Let ID ⊥ AC in D, ie ⊥ BC in E, if ⊥ AB in F, ≁ I be the inner part of triangle, ≁ ad = AF, CD = CE, be = BF, AC + AI = AD + CD + AI = AF + CE + AI = BC = CE + be, ≁ AF + AI = be, take point o on BF, make fo = AF, △ AFI ≌ ofI, ≌ IAF = ≌ IOF, AI = IO, IO + AF = IO + fo = BF & nbsp; ≁ IO = Bo, ≌ EBI = ≌ OIB = ≌ IBF = 1 / 2
Therefore, the answer is: 40 °; 120 °

In the triangle ABC, ab = c.bc = a.ca = b.ad is the angle bisector, I is the heart, then AI is better than id =?

AI ratio id = (c + b) / A; according to the angular bisector theorem, BD / DC = C / B; so BD = (C / (c + b)) a; according to the angular bisector theorem, AI ratio id = C / BD = C / ((C / (c + b)) a) = (c + b) / A

Known: as shown in the figure, in △ ABC, ∠ C = 90 ° AB = 10, BC = 6, P is the intersection of bisectors of ∠ BAC, ∠ ABC, find the distance from point P to ab

Let p be the center of the triangle inscribed circle, let R be the radius, and make PD perpendicular to BC, PE perpendicular to AC, PF perpendicular to ab. then BD = BF = 6-r, AE = AF = 8-r, ab = 10 = BF + AF, so
The distance between P and ab is 2

Using Karnaugh map reduction method to find the simplest and or expression of F (a, B, C, d) = ∑ (1,5,6,7,11,12,13,15)

If there is no wrong circle, it should be: a'c'd + ABC '+ BD + ACD

Reduction of L (a, B, C, d) by Karnaugh map method = ∑ m (0,1,2,5,6,8,9,13,14) + ∑ D (10,11)

L（A,B,C,D）=∑m（0,1,2,5,6,8,9,13,14）+∑d（10,11）
L（A,B,C,D）=∑n（0,1,2,5,6,8,9,10,11,13,14）
Then draw a picture as shown in the figure