Problem 1, solution:

What is the percentage of the total red ribbon: 20%=20/ 100= 1/5.

What is the percentage of yellow ribbon in the total: x/6?

What percentage of the total is blue ribbon: 1- 1/5-X/6 (wrong question: six tenths of x is yellow, X=? )

How many ribbons do you buy at school? 8 1( 1- 1/5-X/6)= 1

Question 2, (1) Solution:

Talk time: 2 hours =60 minutes/hour ×2= 120 minutes. As shown in the figure:

Program a

(1) The call time is less than 60 minutes, and the charge is 98 yuan. (Basic telephone charges)

② If the call time exceeds 60 minutes, each minute will be overcharged: (230 yuan -98 yuan) ÷(500 minutes -60 minutes) =0.3 yuan/minute.

Telephone bill payable for 2 hours (120min): 98 yuan +0.3 yuan/min× (120min-60min) = 1 16 yuan.

Scheme b

① Within 500 minutes, the phone bill should be paid 168 yuan. (Basic telephone charges)

(2) 500 minutes, and 0.3 yuan per minute. (Because MN//CD, the ratio of two straight lines is the same. )

2 hours (120 minutes) phone bill payable: 168 yuan.

Question 2, (2) Solution:

As shown in the figure, the dotted lines of Scheme A and Scheme B intersect at point P, and point P is marked on the figure.

Point P, phone bill payable: 168 yuan.

Talking time: 60 minutes +( 168 yuan -98 yuan) ÷0.3 yuan/minute =293+ 1/3 minutes (≈293 minutes).

Analysis: When the call time is less than 293+ 1/3 minutes, the tariff of Scheme A is low;

When the call time is 293+1/3 minutes, the charges of Scheme A and Scheme B are the same;

When the call time is more than 293+ 1/3 minutes, the tariff of scheme b is low;

Therefore, when the talk time is longer than 293+ 1/3 minutes, Scheme B will be more advantageous than Scheme A. ..

In reality, the billing method of the telecommunications bureau: "If the time is insufficient 1 minute, it will be charged according to 1 minute (billing principle)."

So the answer should be: when the call time exceeds 293 minutes, plan B will be more favorable than plan A.

It is said that because of this, China Telecom and China Unicom will charge tens of billions more user fees every year! ! !