equation

Everyday

1. An equation is a number sentence with an equals sign, showing that two sides have the same value, like 3 + 4 = 7. tree →
2. An equation often has a missing number or letter to find, like x + 2 = 5. tree →
3. In science, an equation is a short way to write a rule or a reaction. tree →

In the lessons

a number sentence that shows the problem, often with a missing number to find; in maths: solving an equation means finding the missing number that makes both sides equal; in science: equations show how things are related; phrases: «solve the equation», «write an equation», «balance the equation»

Examples

• Write an equation for the story. tree →
• Solve the equation 5 + □ = 12. tree →
• The equation x − 4 = 9 means a number take away 4 is 9. tree →
• Which equation matches the problem? tree →
• An equation is like a balance: both sides weigh the same. tree →
• Check your answer by putting it back into the equation. tree →
• 2 + 3 = 5 is an equation, but 2 + 3 is not. tree →
• Einstein's famous equation is E = mc². tree →

Note

Asks to write the operation as a number sentence or to find a missing number; the missing number is found with the opposite operation. Trap: in □ − 4 = 9 add 4 to 9, do not take 4 away. An equation must have an equals sign; whatever you do to one side, do to the other.