There are 357 seniors in Harris High School. The ratio of boys to girls

147 boys, 210 girls

140

To find the number of boys in the senior class, we first need to determine the fraction of the total senior population that represents boys. Since the ratio of boys to girls is given as 7:10, the total ratio is 7 + 10 = 17.

Next, we divide the number of seniors by the total ratio to find the fraction of the total population that represents each "part" of the ratio.

Let's calculate the fraction of the total population that each "part" of the ratio represents:

Fraction for boys = 7 / 17
Fraction for girls = 10 / 17

Now, we can find the number of boys in the senior class by multiplying the total number of seniors by the fraction that represents boys:

Number of boys = Fraction for boys * Total number of seniors
Number of boys = (7 / 17) * 357

Let's calculate that:

Number of boys = (7 / 17) * 357 = 147

So, there are 147 boys in the senior class of Harris High School.