Math

posted by .

Three lighthouses on three nearby islands flash their lights every evening. On one island, the light flashes every 45 seconds. The lighthouse on the second island flashes every 2 minutes. The third lighthouse flahses a light every 1 and 1/4 minutes. Suppose the lights flash together at 8:35pm. At what time will they flahs together agian? Explain your answer.

  • Math -

    First the times in seconds.
    Then least common multiple
    45 seconds, 120 seconds, 75 seconds
    factor them all
    3 *3 * 5
    2 * 2 * 2 * 3 * 5
    3 * 5 * 5
    so we need
    2 * 2 * 2 * 3 * 5 * 5
    thet is
    8*3*25
    =600 seconds
    = 10 minutes

  • Math -

    8:45

  • Math -

    It's actually 2*2*2*3*3*5*5 = 1800 seconds which is 30 minutes. It will be 9:05 when they all flash together again.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. general ability

    light X flashes every 3 minutes. Light Y flashes every 5 minutes. Light Z flashes every 7 minutes. At exactly 7:28 AM they all flash together. At what time will they do so again?
  2. maths

    a light house flashes every 56 seconds. Another lighthouse flashes every 40 seconds. At 9 p.m. they both flash t the same time. What time will it e when they next both flash at the same time?
  3. MATH

    One light flashes every 2 minutes and another light flashes every 3.5 minutes. Suppose both lights flash together at noon. What is the first time after 1 PM that both lights will flash together ?
  4. MATH

    One light flashes every 2 minutes and another light flashes every 3.5 minutes. Suppose both lights flash together at noon. What is the first time after 1 PM that both lights will flash together ?
  5. Math :/

    A light flashes every 15 minutes. a second light flashes every 18 minutes. both lights flash together are 2 a.m. What will the time be when they net flash together?
  6. Math

    the green light flashes every 3 seconds,the red every 5 seconds and white at 10 seconds. iF they flash at 12 noon.When will they flash together again in a minute?
  7. math

    on a radio tower, a red light flashes every 6 seconds and a blue light flashes every 10 seconds. if both lights flash together at a certain time, how many seconds later will both lights flash together the next time
  8. Math

    If a red light flashes every 3 seconds, a blue light flashes every 4 seconds and a blue light flashes every 5 seconds and they all flashed together at midnight when would be the next time they all flash together?
  9. math

    A lighthouse flashes its light every 12 minutes.Another lighthouse flashes every 18 mins. If the two lighhouses flash together at 12:00 noon,at what time will they next flash together?
  10. maths

    a blue light flashes every 8 seconds and a red light flashes every 12 seconds both lights have just flashed together how many secons will they flash together

More Similar Questions