Sieve of Eratosthenes

The Sieve of Eratosthenes is an ancient method for finding all primes numbers up to a specified number.

It was created by Eratosthenes (275-194 B.C., Greece), an ancient Greek mathematician. Just as a sieve is a strainer for draining spaghetti,  Eratosthenes's sieve drains out composite numbers and leaves prime numbers behind. The numbers from 1 to 100 are listed in a table. We will  use The Sieve of Eratosthenes to find all primes up to the number 100 by following the directions below.

Directions:

1. Cross out 1 since it is not prime.
2. Circle 2 because it is the smallest prime number. Cross out every multiple of 2.
3. Circle the next open number, 3. Now cross out every multiple of 3.
4. Circle the next open number, 5. Now cross out every multiple of 5.
5. Circle the next open number, 7. Now cross out every multiple of 7.
6. Continue this process until all numbers in the table have been circled or crossed out.

You have just circled all the prime numbers from 1 to 100!

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Questions (to be answered as a comment):

1. How many prime numbers are there from 1 to 100?
2. List all prime numbers from 1 to 100.
3. Which number is the only even prime number?
4. An emirp (prime spelled backwards) is a prime that gives you a different prime when its digits are reversed. For example, 13 and 31 are emirps. List all emirps between 1 

Enjoy it.

Area and volume of geometric shapes

Hi all,

these days we have been working in class with surface area and volume of some geometric shapes. I leave you here some links to go over the most important ones: Platonic solids (tetrahedron, cube, octahedron, dodecahedron, icosahedron), Pyramid, Prism, Cylinder, cone and sphere.

Remember that you have to present by the end of this week your work including:
1. Name of your shape.
2. Description.
3. Picture.
4. Net (See website to get some ideas).
5. Surface area and volume.
6. Examples in real life.
(Deadline: friday, 30th of november)

If you want to practice or get some ideas or pictures, you can find more exercises here:

• Surface area of a cube, rectangular prism, pyramids and cones, cylinder, cylinder and prism,
• Volume of a cube, rectangular prism, prism and cylinder, triangular prism, cone,  pyramid and cone, cylinder, pyramid, sphere.
• Volume and surface area of sphere

And here I post as well the summary I promised... Download file.

Take care,

ALICIA

Money, Money, Money

When you borrow money from a bank, you pay interest. Interest a fee charged for borrowing the money, it is a percentage charged on the principle amount for a period of a year - usually.

If you want to know how much interest you will earn on your investment or if you want to know how much you will pay above the cost of the principal amount on a loan or mortgage, you will need to understand how compound interest works (See video).

Compound interest is paid on the original principal and on the accumulated past interest.

Practice doing the activity here.

Take care.

My apologies

Pues eso, que mis excusas, espero volver a la carga con energía. Y con buen humor, que parece que la Jefatura de Estudios me tiene un poco borde últimamente... Os dejo una canción de mi época de instituto.