A medicine dose is (15) mg on the first day and increases by (5) mg each next day. What is the dose on the (7)th day?
Answer and explanation
Correct answer: 45 mg
The doses form an arithmetic progression (AP), with first term \(a=15\) mg and common difference \(d=5\) mg. The dose on day \(7\) is \(a_7=a+(7-1)d=15+6\times5=45\) mg. Choosing 40 mg counts only 5 increases, but there are 6 increases from day 1 to day 7. Exam tip: Use \(a_n=a+(n-1)d\) for the \(n\)th term of an AP.
Frequently asked questions
What is the correct answer to this question?
45 mg
Why is this the correct answer?
The doses form an arithmetic progression (AP), with first term \(a=15\) mg and common difference \(d=5\) mg. The dose on day \(7\) is \(a_7=a+(7-1)d=15+6\times5=45\) mg. Choosing 40 mg counts only 5 increases, but there are 6 increases from day 1 to day 7. Exam tip: Use \(a_n=a+(n-1)d\) for the \(n\)th term of an AP.
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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