Idea 13of 23Builds onPut a number in for the letterEquals means the same value
Guess, check and revise
How can you solve an equation by trying numbers?
Today you'll discover
- how one try points to the next
- what too small and too big tell you
- when to stop
Think first3x + 4 = 25: try a number
x = 5 gives 3 × 5 + 4 = 19. What should you try next?
Decide first, then press Next. Use each try to choose the next one.
The equation 3x + 4 = 25 above a table of tries and a number line with a dashed target at 25. Try 5: 3 × 5 + 4 = 19, too small. Try 8: 28, too big. Try 7: 25, just right, ringed on the target. The last step shows 4x + 3 = 35.
See the whole ideathe big idea and the key word, in one place
The big idea
Guess, check and revise: each try tells you to go bigger or smaller.
Three tries
Each try lands closer to 25.
- x = 519too small
- x = 828too big
- x = 725just right
Easy to get wrongClose is not equal: 39 is not 35. Keep revising until both sides match.
Key word
- guess and check
- try a number, check it in the equation, and use the result to choose a better try
Ready to use it?
- Solve an equation by guess, check and revise.