Solving Simple Equations Using Inspection

In this video we’re going to look at how we can solve equations using a method called inspection. An equation is a mathematical sentence with two sides that are equal to each other. We solve equations to find the number or numbers that make the sentence true. x + 3 = 5 is saying “something plus 3 equals 5”. What is the missing number? 2! So x = 2. We have solved the equation by inspection. It just means to look at the question and try and work out the missing number. How can we make the left hand side equal the right hand side? What about this question: 15 + y = 5. What is the missing number? This is a bit of a trick question. 15 plus what gives 5? We actually need to subtract 10. So y = -10. EXAMPLE: 4a = 12. This is saying 4 times a. So what’s the missing number? It must be 3. a = 3. We can still use this same approach for slightly trickier questions. EXAMPLE: 2x - 1 = 5. This is saying something minus 1 equals 5. That something must equal 6. So our unknown 2x equals 6. We can then solve this second bit also just by working it out. Something times 2 equals 6. It must be 3. x = 3.