Here is an easy trick to make long multiplication in just 5 seconds.
Example 1: Calculate 99999999 × 99999999
Step 1: Observe the pattern 9 × 9 = 81
99 × 99 = 9801
999 × 999 = 998001
9999 × 9999 = 99980001
Answer :- 9999999800000001
Example 2: Calculate 12345679 × 81
Step 1: Observe the pattern
12345679 × 9 = 111111111
12345679 × 18 = 222222222
12345679 × 27 = 333333333
12345679 × 36 = 444444444
Answer = 999999999
Example 3: Calculate 666666666 × 666666667
Step 1: Observe the pattern
6×7 = 42
66 × 67 =4422
666 × 667 = 444222
6666 × 6667 = 44442222
Answer: 444444444222222222
10 feb 2014
Ratio proportion problem
The usal method of solving ratio proportion problems may be time consuming with the given trick, you can reduce your problem solving time.
Example:- In equal amounts of time three professors are able to solve problems in the ratio of 1.5 : 2.5 : 3.5, if the professor with the least capability can solve 6 problem in 2 hours, how many problems will the professor with highest ability solve in 3 hours? Assume that they solve problems with uniform speed.
A) 9 b) 10 c) 15 d) 21 e) 25
Step 1: The ratio of solving problems is 1.5 : 2.5 : 3.5 or 3 : 5 : 7, with 7 being the proportion of problems solved by the best professor.
Step 2: Thus the number of problems he solves should be a multiple of 7
Step 3: This condition is met by option 'd' alone.
Answed : d) 21.
3 Feb 2014
Rounding decimal numbers
There are certain rules to round decimals that cannot be overlooked when we round decimals to a certain number, we replace the figure we have with the one that is closest to it. Find out how it can be achieved.
Example: Round 1.25687
to 2 decimal places
Look at the decimal place after 5 (because it is at the second place after decimal)
Case 1: If the number in the next decimal place is > 5, add 1 to the number in the place you have rounded. So the number becomes 1.26
Case 2: If the number in the next decimal place is < 5, we just Write the number out as it to the required number of places.
E.g. 1.254 becames 1.25
26 jan 2014
Trick to add time
For time related problems here is a quick and easy trick to add time. This simple way will teach you to add hours and minutes together.
Step 1: Let's add 1 hour and 35 minutes and 3 hour 55 minutes together.
Step 2: Make 1 hour 35 minutes into one number i.e.135.
Similarly, 3 hours 55 minutes will become 355.
Step 3: Add, 135 + 355 = 490.
Step 4: if the minutes are 60 or more, subtract 60 from minutes;
90 - 60 = 30
And add 1 to hours; 1 + 4 = 5
So the grand total becomes 530
Answer: 5 hrs and 30 minutes.
Here is another example : Add 2 hours 45 minutes and 1 hour 10 minutes
Step 1: The two numbers obtained from time are: 245 and 110.
Step 2: 245 + 110 = 355
Step 3: Here minutes are less than 60, so the total time becomes 3 hours 55 minutes.
14 jan 2014
Convert recurring decimal to fraction
In school Students keep dealing with recurring decimals and their problems. The traditional method is length and time Consuming. Here is a short trick to convert recurring decimals to fractions.
Say the number is 2.1363636.....
Step 1: First ignore the digit on the left digit of decimal I.e 2.
Step 2: The denominator will be 990.
(To get the denominator of the fraction, we need to use 9s for each digit of the repeating part. The fixed digit(s) is offset by putting a trailing Zero (990)
Step 3: For the numerator, subtract the fixed part from the number (without repetition).
Numerator = 136 - 1 = 135
Step 4: The digit 2, which was ignored earlier will simply be added to the left of the resultant fraction.
Step 5: Answer : 2 (135/990)
Now you try it.
Find fraction of 0.4444............