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Reward math problems
1. The circular area is 6.28 square centimeters.

The distance between the two toes of the compass is 4 cm.

The three internal angles and degrees of this triangle are 140, 40 and 40 respectively.

1.∫3.5-meter-long rope wraps around the trunk five times, leaving 0.36 meters.

The circumference of trunk is (3.5-0.36) ÷ 5 = 0.628m..

The radius of trunk is 0.1m.

∴ The area of the trunk section is πr? =3. 14×0. 1? =0.03 14m?

A: The cross-sectional area of the trunk is 0.03 14 square meter.

2.200×6000×3×0.5%= 18000 yuan

A: The insurance premium payable by the school is18,000 yuan.

3. Set this book to ***x pages.

1/3x+(x- 1/3x)×3/5+(x- 1/3x)×3/5- 10 = x

x=75

This book has 75 pages.

4. Let the speed of car A be x, then the speed of car B is 3/2x.

x×0.6+3/2x×0.6= 120

x=80

A: The speed of car A is 80 kilometers per hour.

Suppose Xiaoming reads a book and has read X pages, then he hasn't read 5x pages.

Then look at it after 30 pages.

(x+30)/(5x-30)=3:5

x=24

So I have read 24 pages, but I haven't read 120.

So this book ***24+ 120= 144 pages.

A: This book *** 144 pages.