Here are three lamps. lamp C
lamp B
lamp A
Lamp A flashes every 20 seconds.
Lamp B flashes every 45 seconds.
Lamp C flashes every 120 seconds.
The three lamps start flashing at the same time.
How many times in one hour will the three lamps flash at the same time?

Answer with step-by-step explanation:

First of all, we need to calculate how many times the 3 lamps flash in a minute. We can do this by finding their LCM (least common multiple), which is 360. 360 is equivalent to 6 minutes, so that is going to be our test time. Lamp a flashes every 20 seconds, so 360/20 = 18 flashes. Then, 360/45 = 8 flashes. Finally, 360/120 = 3 flashes. 18 + 8 + 3 = 29 flashes per 6 minutes. If so, we multiply 29 by 10, because 60 minutes per hour ÷ 6 minutes = 10. So 29 × 10 = 290 flashes per hour

Hope this helped! (brainliest please)

answer: l

step-by-step explanation:

38.5

step-by-step explanation:

lets say, first number = r

second number = 3r+7

total = 49

(r)+(3r+7)= 49

4r+7 = 49

4r = 42

r = 42/4

r= 10.5

3r+7 = 3(10.5)+7 = 38.5

hope this