Being able to do multiplication using your fingers is a useful skill and a method that has been in use since at least the 15th century. Your mobile phone probably has a built-in calculator, but in some cases it is more convenient to keep the device in your pocket and proceed manually. It is also a supportive technique for students learning to do this for the first time. For this to work, you need to know multiplication tables from one to five, because finger multiplication is applicable to times tables of six, seven, eight, nine and ten.
Steps
Part 1 of 2: Multiply by Nine
Step 1. Hold your hands in front of you with palms facing up
Each finger represents a number; count from 1 to 10, starting with the left thumb up to the right.
Step 2. Bend the finger corresponding to the number you want to multiply by nine towards your body
For example, if you want to solve the multiplication 9x3, you have to bend the left middle finger; this finger represents the number 3 because, if you count from 1 to 10 starting with the left thumb, the middle finger occupies the third position.
Step 3. Solve the task by counting the fingers left and right
First count those that are to the left of the bent finger - in the case considered as an example they are 2. Then count those that are to the right of the bent finger - based on the example described above, it is 7 fingers. The first digit of the result is 2, the second is 7, the solution is therefore 27!
Step 4. Try this method with other multiples of 9
What is the solution of 9x2 and 9x7?
Part 2 of 2: Multiply by Six, Seven, Eight and Ten
Step 1. Hold your hands in front of you with palms facing your body, while your fingers are placed in front of each other
Again, each finger represents a number. Little fingers are number 6, ring fingers are 7, middle fingers are number 8, index fingers are number 9 and inches are 10.
Step 2. Join the fingers representing the multiplication factors
For example, if you want to solve the 7x6 operation, you have to touch the left ring finger with the right little finger. The fingers of the left hand represent the first factor of the multiplication (the one on the left) and the fingers of the right hand the second factor (the one on the right). Remember that also for this method each finger represents a number: the ring finger corresponds to 7 and the little finger to 6; consequently, you have to put your fingers in contact with each other to solve the arithmetic problem.
- You probably have to bend your wrist abnormally to do this.
- As another example, if you want to calculate 9x7, you have to touch the left index finger with the right ring finger.
Step 3. Count how many fingers are touching and how many are under them
In this particular step, each finger is worth 10. Considering the previous example (7x6), you have to add the left ring finger, the left little finger and the right little finger, ie 3 fingers: since each finger is worth 10, the total is 30.
Step 4. Multiply the number of remaining fingers
The next step is to add the fingers of each hand, leaving out those in contact. Start with the fingers of the left hand that are above the one in contact - in the example described there are 3. Then count the number of fingers of the right hand that are above the one in contact - in this case they are 4. At this point, proceed to multiplication 3x4 = 12.
Step 5. Add the two values you found to get the solution
In the example described, you got 30 and 12, for a total of 42. So, the solution to the 7x6 operation is 42.
Step 6. Do the multiplication by 10 using the same technique
For example, if you want to find the 10x7 solution, start by joining your left thumb to your right ring finger. Count the number of fingers below those in contact, including these in the count. The total should be 7; remember that in this step they represent the value of the tens, so the result is equal to 70. Now count the number of fingers that are above the fingers in contact; they should be 0 for the left hand and 3 for the right hand. Multiply 0x3 to get 0, then add 0 to 70 and the result is 70. The solution of 10x7 is 70!
Step 7. Try this method for calculating multiples of 6, 7, 8 and 9
How much is 8x8? What about 7x10?
