In the sequence (100,96,89,x,66), the differences are (-4,-7,-10,-13). What will (x) be?
Answer and explanation
Correct answer: 79
The consecutive differences are \(-4,-7,-10,-13\). Therefore, adding \(-10\) to the third term gives \(x=89-10=79\). Check: \(79+(-13)=66\), so the next difference is also satisfied. If 76 were chosen, the difference from 89 would be \(-13\), not the required third difference of \(-10\). Exam tip: a negative difference means subtract that value from the preceding term.
Frequently asked questions
What is the correct answer to this question?
79
Why is this the correct answer?
The consecutive differences are \(-4,-7,-10,-13\). Therefore, adding \(-10\) to the third term gives \(x=89-10=79\). Check: \(79+(-13)=66\), so the next difference is also satisfied. If 76 were chosen, the difference from 89 would be \(-13\), not the required third difference of \(-10\). Exam tip: a negative difference means subtract that value from the preceding term.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Sequences.
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