Handy Maths Tricks Using Only Your Hands!

Handy Maths Tricks Using Only Your Hands!

Ever struggle with remembering things? Use these tricks to help you to remember your times tables, the number of days in a month, and even the sine of an angle.

#1: 9 times table

Here is a well known one to start us off.

1. Hold out both your hands. Number your fingers from 1 to 10, going left to right.
2. You want to multiply 9 by some number less than or equal to ten. Fold down the finger corresponding to this number.
3. The number of the fingers to the left of the folded down finger is the first digit and the number of fingers to the right is the second digit. This is your answer!

Note: If there are no fingers to one side of the folded down finger then that digit is simply 0, as there are no fingers.

#2: How many days in a month?

I haven t seen this trick as often, and technically it is not maths, but I find it very useful!

1. Hold your clenched fists out.
2. Starting from the left, count the months January, February, along the knuckles and the space between the knuckles, until you reach your target month.
3. If you landed on a knuckle then the number of days in that month is always 31. If you landed in-between then it will be 30 (unless it is February, which goes by its own rules!).

Now you only need to remember that February has 28 days, unless it is a leap year when it has 29 days.

#3: Trick for 6, 7, 8, 9, 10 times tables

A neat trick for calculating your times tables in an interesting way, even though it is a little overcomplicated!

1. Starting from your little finger, label your fingers 6, 7, 8, 9, 10 on both hands.
2. Touch the two fingers together, one from each hand, corresponding to the two numbers that you are multiplying together.
3. On your left hand, count the number of fingers including and below the touching finger. Repeat for your right hand.
4. Add these numbers together and multiply by 10. Call this number x.
5. On your left hand, count the number of fingers above (not including) the touching finger. Repeat for your right hand.
6. Multiply these two numbers together. Call this number y.
7. Add x and y together to get your answer.

#4: Calculate the sin, cos and tan of some angles without a calculator!

This trick can be difficult but it only requires one hand, and it can be useful for remembering the answers to common sin, cos and tan calculations.

1. Starting from the thumb, label each finger with the values: 0, 30, 45, 60, 90 degrees
2. Fold down the finger corresponding to the angle that you are calculating
3. The number of fingers on the thumb side is for sin, and the other side for cos. Note the number of fingers depending on whether you are calculating sin or cos.
4. Take that number, square root it and divide by 2. That is, sqrt(x)/2. Simplify if you can but otherwise leave it.

That s it! Using this trick you can find the sin or cos of 0, 30, 45, 60, and 90 degree angles.

For the tan of the angle, the answer is: sqrt(x)/sqrt(y)

where: x = the number of fingers on the thumb side

y = the number of fingers on the opposite side

Can you see why? Hint below:

Use tan = sin/cos