Using symbols instead of numbers What number can be added to 21 to get 50? + 15 = 277 x = 56 Sometimes questions have a missing number that you need to find.

Using symbols instead of numbers What number can be added to 21 to get 50? = 277 x 8 = 56 Sometimes questions have a missing number that you need to find.

Using symbols instead of numbers We often use a symbol to represent that missing number. Sometimes this is a letter. P + 43 = 804 x n = 24

Using symbols instead of numbers We can use a variety of strategies to solve these: TRIAL & ERROR TRIAL & IMPROVEMENT INVERSES

Using symbols instead of numbers TRIAL & ERROR – also known as guesswork! This is the most basic method. Guess various numbers and see if they work. It is not very efficient and doesnt always give you the answer w = 94

Using symbols instead of numbers TRIAL & ERROR – also known as guesswork! This is the most basic method. Guess various numbers and see if they work. It is not very efficient and doesnt always give you the answer w = 9480?

Using symbols instead of numbers TRIAL & ERROR – also known as guesswork! This is the most basic method. Guess various numbers and see if they work. It is not very efficient and doesnt always give you the answer w = 9480? x

Using symbols instead of numbers TRIAL & ERROR – also known as guesswork! This is the most basic method. Guess various numbers and see if they work. It is not very efficient and doesnt always give you the answer w = 9470?

Using symbols instead of numbers TRIAL & ERROR – also known as guesswork! This is the most basic method. Guess various numbers and see if they work. It is not very efficient and doesnt always give you the answer w = 9470? x

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9480?gives 106 – too big! So lets look at numbers less than 80.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9470?gives 96 – too big! So lets look at numbers less than 70.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9460?gives 86 – too small! So lets look at numbers between 60 and 70.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9465?gives 91 – too small! So lets look at numbers between 65 and 70.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9467?gives 93 – too small! So lets look at numbers between 67 and 70.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9469?gives 95 – too big! So lets look at numbers between 67 and 69.

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 9468?Gives 94 – correct!

Using symbols instead of numbers TRIAL & IMPROVEMENT – educated guesswork that gets more accurate! This method usually gets you to the answer, but can take a long time. It helps if you say if the answer is too big, too small, or correct w = 94w = 68

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier w = 94 The INVERSE of + is -

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier. w = The INVERSE of + is -

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier. w = 68 The INVERSE of + is -

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier. d x 9 = 54 The inverse of x is ÷

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier. d = 54 ÷ 9 The inverse of x is ÷

Using symbols instead of numbers INVERSES – using the undo method. This method will always get you the answer, and will often be the quickest method. It is, however, slightly trickier. d = 6 The inverse of x is ÷

Using symbols instead of numbers Try these: 6 + a = 19 b + 43 = – c = 2Be careful with these ones d – 26 = 90 e x 4 = 32 7 x f = 77 g ÷ 10 = ÷ h = 6

Using symbols instead of numbers Try these: 6 + a = 19a = b + 43 = 60b = 15 – c = 2c = d – 26 = 90d = e x 4 = 32e = 7 x f = 77f = g ÷ 10 = 120g = 300 ÷ h = 6h =

Using symbols instead of numbers Try these: 6 + a = 19a = b + 43 = 60b = 60 – – c = 2c = d – 26 = 90d = e x 4 = 32e = 32 ÷ 4 7 x f = 77f = 77 ÷ 7 g ÷ 10 = 120g = 120 x ÷ h = 6h = 300 ÷ 6

Using symbols instead of numbers Try these: 6 + a = 19a = 13 b + 43 = 60b = – c = 2c = 13 d – 26 = 90d = 116 e x 4 = 32e = 8 7 x f = 77f = 11 g ÷ 10 = 120g = ÷ h = 6h = 50