A reservoir has (1000) litres of water on the first day and (50) litres less each day. How much water remains on the (8)th day?
Answer and explanation
Correct answer: 650 litres
The water amounts form a decreasing arithmetic progression, with first term \(a=1000\) and common difference \(d=-50\). On the eighth day, \(a_8=a+(8-1)d=1000+7(-50)=650\) litres. Choosing \(600\) litres would subtract 50 eight times, but the given amount is already for day 1. Exam tip: use \(a+(n-1)d\) for the \(n\)th term.
Frequently asked questions
What is the correct answer to this question?
650 litres
Why is this the correct answer?
The water amounts form a decreasing arithmetic progression, with first term \(a=1000\) and common difference \(d=-50\). On the eighth day, \(a_8=a+(8-1)d=1000+7(-50)=650\) litres. Choosing \(600\) litres would subtract 50 eight times, but the given amount is already for day 1. Exam tip: use \(a+(n-1)d\) 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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