A worker lays (30) bricks on the first day and (6) more bricks each next day. How many bricks will he lay on the (9)th day?
Answer and explanation
Correct answer: (78)
The number of bricks laid each day forms an AP with first term \(a=30\) and common difference \(d=6\). For the ninth day, \(a_9=a+(9-1)d=30+8\times6=78\). Therefore, the correct answer is (78). (84) would result from adding 6 nine times to 30, but there are only 8 increases after the first day. Exam tip: use \((n-1)d\) in the formula for the \(n\)th term.
Frequently asked questions
What is the correct answer to this question?
(78)
Why is this the correct answer?
The number of bricks laid each day forms an AP with first term \(a=30\) and common difference \(d=6\). For the ninth day, \(a_9=a+(9-1)d=30+8\times6=78\). Therefore, the correct answer is (78). (84) would result from adding 6 nine times to 30, but there are only 8 increases after the first day. Exam tip: use \((n-1)d\) in the formula for the \(n\)th term.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Word problems based on APs.
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