Discussion
What is the value of \((39)^{2} - (38)^{2}\) ?
Answer: A
Use the identity for the difference of two squares, which says that a squared minus b squared equals (a + b) times (a - b).
\[ 39^{2} - 38^{2} = (39 + 38)(39 - 38) \]
\[ = 77 \times 1 = 77 \]
So the value is 77, option (A). A check: 39 squared is 1521 and 38 squared is 1444, and their difference is 77. The values 108, 117 and 57 come from adding or subtracting the numbers instead of using the identity correctly. The identity is also used to calculate in the head: any difference of the squares of two consecutive numbers is the sum of the two numbers.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development