Simple tricky math quiz 5

     

Operations

"Operations" mean things like add, subtract, multiply, divide, squaring, etc. If it isn"t a number it is probably an operation.

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But, when you see something like ...

7 + (6 × 52 + 3)

... what part should you calculate first?Start at the left and go to the right?Or go from right to left?

Warning: Calculate them in the wrong order, and you can get a wrong answer !

So, long ago people agreed to follow rules when doing calculations, and they are:

Order of Operations

Do things in Parentheses First

4 × (5 + 3) = 4 × 8 =
4 × (5 + 3) = 20 + 3 =
(wrong)

Exponents (Powers, Roots) before Multiply, Divide, Add or Subtract

5 × 22 = 5 × 4 =
5 × 22 = 102 =
(wrong)

Multiply or Divide before you Add or Subtract

2 + 5 × 3 = 2 + 15 =
2 + 5 × 3 = 7 × 3 =

Divide and Multiply rank equally (and go left to right).

Add and Subtract rank equally (and go left to right)


*

After you have done "P" and "E", just go from left to right doing any "M" or "D" as you find them.

Then go from left to right doing any "A" or "S" as you find them.

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You can remember by saying "Please Excuse My Dear Aunt Sally".

Or ... Pudgy Elves May Demand A SnackPopcorn Every Monday Donuts Always SundayPlease Eat Mom"s Delicious Apple StrudelsPeople Everywhere Made Decisions About Sums

You may prefer GEMS (Grouping, Exponents, Multiply or Divide, Add or Subtract).In the UK they say BODMAS (Brackets, Orders, Divide, Multiply, Add, Subtract).In Canada they say BEDMAS (Brackets, Exponents, Divide, Multiply, Add, Subtract). It all means the same thing! It doesn"t matter how you remember it, just so long as you get it right.

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Examples


Example: How do you work out 3 + 6 × 2 ?

Multiplication before Addition:

First 6 × 2 = 12, then 3 + 12 = 15


Example: How do you work out 12 / 6 × 3 / 2 ?

Multiplication and Division rank equally, so just go left to right:

First 12 / 6 = 2, then 2 × 3 = 6, then 6 / 2 = 3


*

Example: Sam threw a ball straight up at 20 meters per second, how far did it go in 2 seconds?

Sam uses this special formula that includes the effects of gravity:

height = velocity × time − (1/2) × 9.8 × time2

Sam puts in the velocity of 20 meters per second and time of 2 seconds:

height = 20 × 2 − (1/2) × 9.8 × 22

Now for the calculations!


Exponents of Exponents ...

What about this example?

432

Exponents are special: they go top-down (do the exponent at the top first). So we calculate this way:

Start with: 432
32 = 3×3: 49
49 = 4×4×4×4×4×4×4×4×4: 262144

So 432 = 4(32), not (43)2

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