prolem solving question
I'm having a tought time solving this problem:
The 100W light bulb (cost €0.60) is not going to be used anymore and is being replaced with the
20W (cost €3) low energy light bulb.
If electricity is charged at €0.15 per kWh, for how many hours must the low energy bulb be used in
order for the lower cost of running it to exactly compensate for its higher initial cost?
A 160.00
B 0.25
C 200.00
D 250.00
E 720.00
The correct answer is A but I can't seem to understand why, I keep getting C.
here's my thought process:
100W/h=0.01kWh, 20W/h=0.02kWh
0.1*0.15=0.015€/h, 0.02*0.15=0.003€/h
t- amount of hours running
(0.015*t)+0.6=(0.003*t)+3
0.012t=2.4
t=200
The 100W light bulb (cost €0.60) is not going to be used anymore and is being replaced with the
20W (cost €3) low energy light bulb.
If electricity is charged at €0.15 per kWh, for how many hours must the low energy bulb be used in
order for the lower cost of running it to exactly compensate for its higher initial cost?
A 160.00
B 0.25
C 200.00
D 250.00
E 720.00
The correct answer is A but I can't seem to understand why, I keep getting C.
here's my thought process:
100W/h=0.01kWh, 20W/h=0.02kWh
0.1*0.15=0.015€/h, 0.02*0.15=0.003€/h
t- amount of hours running
(0.015*t)+0.6=(0.003*t)+3
0.012t=2.4
t=200
Solve
I get
I get
Original post by alextav
Thanks for helping guys.
So there is no way that the answer is A even though it the official answer on the answer key?
So there is no way that the answer is A even though it the official answer on the answer key?
doesn't look like it
Quick Reply
Related discussions
- changing a level subjects
- Isaac physics quantum mechanics primer difficulty level
- How to revise maths w pmt
- Geography Water Cycle
- How to solve this standing wave problem?
- Computer Science Paper 2 (OCR A Level)
- Oxbridge mathematics supercurriculars, 2025 entry
- New semester new start
- An inequation
- Send me your maths questions!
- How do i improve physics problem solving?
- UKMT Senior challenge
- Tips for A*s?
- Need help with this question
- Matrices question
- Maths Problem Solving
- Higher biology and chemistry help!!
- [CIE] [A Level Further Mathematics] Help needed with solving this question EX 1A, #3.
- weird cosine question
- Higher chemistry
Latest
Trending
Last reply 4 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
Edexcel A Level Mathematics Paper 2 unofficial mark scheme correct me if wrongMaths
71
Trending
Last reply 4 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
Edexcel A Level Mathematics Paper 2 unofficial mark scheme correct me if wrongMaths
71
