- LPU MCA Semester 1
- PEA515
- Unit 2
PEA515 · Unit 2: Percentage and profit and loss
Calculation of percentage, comparison and conversion to fractions
30 practice questions · in the MTE and ETE syllabus
Key points
- x% of y = y% of x
- Percentage change uses the original value as the base
- 25% more than B means B is 20% less than A
- Memorise fraction and percentage pairs
Percent means per hundred: x% of y = x y / 100, and x% of y equals y% of x, which is handy for mental maths (8% of 50 = 50% of 8 = 4).
Learn the fraction equivalents: 1/2 = 50%, 1/3 = 33 1/3%, 1/4 = 25%, 1/5 = 20%, 1/6 = 16 2/3%, 1/8 = 12.5%, 1/9 = 11 1/9%, 1/10 = 10%, 1/12 = 8 1/3%.
Percentage change = (new - old)/old x 100. The base is always the quantity that comes after the words "than" or "of". If A is 25% more than B, then A = 1.25 B, but B is only 20% less than A.
To compare quantities, convert to the same base: 3/8 = 37.5% is greater than 35%.
Exam trap: using the new value as the base when the question says "more than the old".
Try two questions
Find 60 percent of 160.
- 266.67
- 960
- 96
- 64
Show the answer
C. Worked answer: 60/100 x 160 = 96.
Why not A: Divides by the percentage instead of multiplying.
Why not B: Divides by 10 instead of 100.
Why not D: Gives the remainder after removing the percentage.
If 32 percent of the total pages is 64, how many pages are there in all?
- 20.48
- 210
- 84.48
- 200
Show the answer
D. Worked answer: Number = 64 x 100 / 32 = 200.
Why not A: Multiplies by the rate instead of dividing by it.
Why not B: Slips by an extra amount after the division.
Why not C: Treats the part as if it were an increase on the whole.