QUARTER FINAL STAGE 2025
GSTS: 39 points (Winner)
PRESEC, Legon: 38 points
OLAG: 28 points
ROUND 2 - SPEED RACE
QUESTION
What is the resistance of a colour-coded resistor marked with three red bands?
ANSWER: 2.2 kΩ
SOLUTION:
Rule: For standard resistor color coding, Red represents the value 2.
For a three-band resistor, the sequence maps directly to the first digit, second digit, and the power of ten multiplier:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Substitute the value 2 for each red band:
$R = 22 \times 10^2\ \Omega$
$R = 22 \times 100\ \Omega$
$R = 2200\ \Omega$
$R = 2.2\text{ k}\Omega$
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PRACTICE QUESTIONS
1. QUESTION: What is the resistance of a colour-coded resistor with bands yellow, violet and red?
ANSWER: 4.7 kΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Yellow = 4, violet = 7, red = 2
$R = 47 \times 10^{2}\ \Omega$
$R = 4.7 \times 10^{3}\ \Omega$
$R = 4.7\text{ k}\Omega$
2. QUESTION: What is the resistance of a colour-coded resistor with bands green, blue and red?
ANSWER: 5.6 kΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Green = 5, blue = 6, red = 2
$R = 56 \times 10^{2}\ \Omega$
$R = 5.6 \times 10^{3}\ \Omega$
$R = 5.6\text{ k}\Omega$
3. QUESTION: What is the resistance of a colour-coded resistor with bands red, violet and orange?
ANSWER: 27 kΩ or $2.7\times10^{1}$ kΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Red = 2, violet = 7, orange = 3
$R = 27 \times 10^{3}\ \Omega$
$R = 27\text{ k}\Omega$
4. QUESTION: What is the resistance of a colour-coded resistor with bands grey, red and red?
ANSWER: 8.2 kΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Grey = 8, red = 2, red = 2
$R = 82 \times 10^{2}\ \Omega$
$R = 8.2 \times 10^{3}\ \Omega$
$R = 8.2\text{ k}\Omega$
5. QUESTION: What is the resistance of a colour-coded resistor with bands brown, green and green?
ANSWER: 1.5 MΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Brown = 1, green = 5, green = 5
$R = 15 \times 10^{5}\ \Omega$
$R = 1.5 \times 10^{6}\ \Omega$
$R = 1.5\text{ M}\Omega$
6. QUESTION: What is the resistance of a colour-coded resistor with bands yellow, violet and black?
ANSWER: 47 Ω or $4.7\times10^{1}$ Ω
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Yellow = 4, violet = 7, black = 0
$R = 47 \times 10^{0}\ \Omega$
7. QUESTION: What is the resistance of a colour-coded resistor with bands blue, grey and black?
ANSWER: 68 Ω or $6.8\times10^{1}$ Ω
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Blue = 6, grey = 8, black = 0
$R = 68 \times 10^{0}\ \Omega$
8. QUESTION: What is the resistance of a colour-coded resistor with bands orange, white and red?
ANSWER: 3.9 kΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Orange = 3, white = 9, red = 2
$R = 39 \times 10^{2}\ \Omega$
$R = 3.9 \times 10^{3}\ \Omega$
$R = 3.9\text{ k}\Omega$
9. QUESTION: What is the resistance of a colour-coded resistor with bands red, violet and green?
ANSWER: 2.7 MΩ
SOLUTION:
$R = (\text{Band}_1\text{Band}_2) \times 10^{\text{Band}_3}$
Red = 2, violet = 7, green = 5
$R = 27 \times 10^{5}\ \Omega$
$R = 2.7 \times 10^{6}\ \Omega$
$R = 2.7\text{ M}\Omega$