Solving a problem often involves making a decision between two or more options. In an algorithm this process of making a decision is called selection.

Describe, in plain english, an algorithm for;

1. Moving through a set of traffic lights.
2. Deciding whether to take an umbrella to school.
3. Giving a student an A, B or C on their test

Moving through a set of traffic lights:

1. Approach the traffic lights.

2. If the light is green then proceed in the direction you intend to go in. If the light is yellow then slow down and prepare to stop (or as other people say, "speed up") If the light is red then stop at the line at the traffic lights.

3. After stopping at red, when the light turns green, proceed in the direction intended.

Deciding whether to take an umbrella to school:

1. Go outside and look at the sky. Check for for dark cloud cover.

2. If there is dark cloud cover, bring an umbrella with you.

Giving a student an A, B or C on a test:

1. Use the marking criteria to allocate marks.

2. Add up marks in each section and whichever has more marks is the correct grade.

Often an algorithm will often require you to repeat a task in order to solve a problem; when this is done in an algorithm the structure is called repetition.

Describe, in plain english, an algorithm for;

1. Adding the correct amount of cordial to water to make a drink.
2. Filling a bucket with water.
3. Blowing up a balloon.

Adding the correct amount of cordial to water to make a drink:

1. Add the directed amount of water as specified by the bottle of cordial.

2. Add the directed amount of cordial as specified by the bottle of cordial.

Filling a bucket with water:

1. Place an empty bucket under a tap.

2. Open the tap and let the water fill the bucket.

3. When the bucket is filled to the desired amount, close the tap.

Blowing up a balloon:

1. Stretch the balloon and place the end between your lips with the hole in line of your blow.

2. Blow into the balloon until the balloon expands to its full potential.