If a and b are both positive, two-digit integers, is a + b a multiple of 11? the tens digit of a is equal to the units digit of b, and the tens digit of b is equal to the units digit of a both a and b are odd.

Yes!

Step-by-step explanation:

Let x be the tens place and y be the units place. x and y need to be odd because in other case a or b will not be odd. For example, if x=1 and y=2 a will be 21 but b will be 12 that is not odd.

Now, a+b = xy+yx. Note that xy is not x*y, is just the digits concatenated.Then, there are two cases:

If x+y<10 then xy+yx = (x+y)(x+y) (again, that is not a multiplication is x+y concatenated with x+y) and that is 11*(x+y) a multiple of 11.

If x+y≥10 then xy+yx = (x+y+1)(x+y-10) because x+y<20.

Now we are going to see that last result without the concatenation, as a sum, that is

(x+y+1)*10 + x+y-10 = 10x+10y+10+x+y-10 = 11x+11y = 11(x+y). This result is clearly a multiple of 11.

In conclusion, in all cases the result of a+b is a multiple of 11.

x = central angle apc = measure of minor arc ac

the two angles x and 30 add to 180, so x+30 = 180 and x = 180-30 = 150. the measure of minor arc ac is 150 degrees.

what we need to do from here is find the circumference and then multiply it by x/360 since there are 360 degrees in a circle. in this case, x = 150, so x/360 = 150/360 = 15/36 = 5/12. the shortest distance along the curve from a to c is 5/12 of the distance around the entire circle (aka circumference)

c = circumference

c = pi*d

c = pi*24

c = 24pi

now multiply this by 5/12 to get

distance along minor arc ac = (5/12)*(circumference)

distance along minor arc ac = (5/12)*(24pi)

distance along minor arc ac = 10pi

the formula you can use is

l = (x/360)*pi*d

with

l = length of minor arc

x = central angle

d = diameter

which essentially is the steps we took though a bit differently.