Question

Mrs. Bennett has graded 20% of her 150 students' papers. How many papers does she still have to finish grading.

Answer 1

Hint: Use percentage formula to solve the questions.
Percentage: Percentage formula is used to find the amount or share of something in terms of hundred.in simplest form percent means per hundred. For expressing something in percent one needs to find the amount or share in 100. To express a number between zero and one percentage formula is used. It is also defined as a number represented as a fraction of hundred. Percentage is denoted by the symbol % and is commonly used to compare and find out ratios. Things to remember for percentage is to calculate the fraction in hundred.

Formula Used:
To calculate p% of q , use the percentage formula as,
$\left( {\dfrac{p}{{100}} \times q} \right)$

Complete step-by-step answer:
Step: Calculate how many she has done already.
Since in the given question she has graded only 20% of 150 paper.
So calculate 20% of 150 by applying the percentage formula.
$\dfrac{{20}}{{100}} \times 150 = 30$
$ \Rightarrow $30 papers are done.
Step: 2 to find the left papers subtract the done papers from total papers.
She has graded 30 papers and total papers are 150.
Therefore left papers for grading
$
   = 150 - 30 \\
   \Rightarrow 120 \\
 $
Therefore 120 papers are still left for grading.

Therefore 120 papers are still left.

Note:
 Students are advised to learn the concept of percentage. They can start by either calculation of how many she has done already, or by calculating what percentage is left still to do. Students should remember that p% of q is equal to q% of p. Students are advised to not make mistakes in calculation.