Answer:
40
Step-by-step explanation:
Let the number of boys participating in the quiz be b and the number of girls be g. Since the total number is 100, we have our first equation.
b + g = 100
The average score was 76 points. This means the total score was 76 * 100 = 7600
The average score for the boys was 80 meaning total scores for the boys was 80b while that of the girls was 70g
Hence, we have our second equation:
80b + 70g = 7600
Now let’s put the equations together and solve simultaneously to get g which is the number of girls:
b + g = 100
80b + 70g = 7,600
Let’s simply make a substitution. We can say b = 100 - g. Substituting this will yield:
80(100 - g) + 70g = 7,600
8000 - 80g + 70g = 7600
10g = 400
g = 400/10 = 40
