Congcong made a round greeting card for her teacher with colored cardboard. In order to be beautiful, she bought a colored rope to stick it to the outside of the card. The card shared 31.4cm colored rope. Do you know how many square centimeters of colored cardboard she used? Come on. Give me the answer in 6 minutes

Congcong made a round greeting card for her teacher with colored cardboard. In order to be beautiful, she bought a colored rope to stick it to the outside of the card. The card shared 31.4cm colored rope. Do you know how many square centimeters of colored cardboard she used? Come on. Give me the answer in 6 minutes

Perimeter = π d = 31.4, so the diameter of the paperboard is d = 31.4 / π, take π = 3.14, then d = 10 (CM)
The area of paperboard is π (D / 2) ^ 2 = 25 π≈ 78.5 (square centimeter)

On 2009 teacher's day, Xiao Hong made a semicircle greeting card for her teacher with colored paper
For the sake of beauty, she specially bought a color rope to make the periphery. The 41.12cm color rope was used to make this card. How many cm color paper plates did she use?

S=8*8*3.14=100.48
That should be square centimeter

How to make teacher's Day cards
The day after tomorrow is teachers' day. Please think about how to make greeting cards for me

The next is the production process, first prepare colored paper ~ not too wide, 0.5cm can be ~ color according to their own needs to set the card, do the card with a sharp knife, glue choose a color to make flowers ~ I chose red to cut the paper apart, cut it into about 4cm long, then cut the dark paper into a good shape, paste it on the light color card to cut

Xiao Ming and Xiao Li have several cards (different number) in their hands. If they give Xiao Ming three cards to Xiao Li, then the number of cards in their hands is the same. If they give Xiao Ming two more cards to Xiao Li, then the number of cards in Xiao Ming's hands is 3 / 5 of Xiao Li's. how to find out the number of original cards in Xiao Ming's and Xiao Li's hands? Let Xiao Ming have X cards

x-3--2=（x-3+2）*3/5
x-5 = 3/5*（x-1）
2x =22
x=11