According to time = distance, the sum of the speeds of two cars can be found.
Solution: 650(70+60),
=650÷ 130,
=5 (hours),
Answer: Meet in 5 hours.
2. Make a square with a metal wire, and its side length is 9.42 cm ... If you make a circle with this wire, what is the area of this circle?
Solution: The circumference of a square is 9.42×4=37.68 (cm).
The radius of the circle: 37.68÷3. 14÷2=6 (cm),
Area of circle: 3.14× 62 =113.04 (square centimeter);
Answer: The area enclosed by a circle is 1 13.04 square centimeters.
3. A flower bed with a diameter of 5 meters is surrounded by a circular cobblestone path with a width of 1 meter. What is the area of this path?
Solution: According to the meaning of the question, r=5÷2=2.5 (meters), R=5÷2+ 1=3.5 (meters),
S ring =π(R2-r2)
=3. 14×(3.52-2.52)
=3. 14×( 12.25-6.25)
=3. 14×6
= 18.84 (m2);
A: The path area is 18.84 square meters.
4. A highway maintenance team plans to build a highway with a length of 1200m. The first week 15% of the total length was completed, and the second week was completed?
1
three
How many meters is the first week less than the second week?
Solution: 1200×
13
- 1200× 15%,
=400- 180,
=220 (meters);
Answer: The first week is 220 meters less than the second week.
The wheel diameter of bicycle is 0.6 meters. If the wheel rotates 100 times per minute on average, how many meters can you ride in half an hour?
Solution: Half an hour =30 minutes,
Wheel speed: 3. 14×0.6× 100,
= 1.884× 100,
= 188.4 (m);
Driving distance: 188.4×30=5652 (m);
A: You can do 5652 meters in half an hour (30 minutes).
Hmm. How interesting