An international scientific symposium begins at 11:15\text{ AM} local solar time in City P… — JAMB UTME

An international scientific symposium begins at $11:15\text{ AM}$ local solar time in City P, located at longitude $40^\circ\text{E}$ . At what local solar time does the symposium begin for a participant watching live from City Q, located at longitude $15^\circ\text{W}$ ?

$07:35\text{ AM}$ Answer
B
$02:55\text{ PM}$
C
$09:35\text{ AM}$
D
$12:55\text{ PM}$

Answer

07:35\text{ AM}

To find the time at City Q (

15^\circ\text{W}

) given the time at City P (

40^\circ\text{E}

), first calculate the total angular separation across the Prime Meridian:

40^\circ + 15^\circ = 55^\circ

. Multiplying by

4\text{ minutes per degree}

gives a total time difference of

220\text{ minutes}

, which equals

3\text{ hours } 40\text{ minutes}

. Because City Q is located to the west of City P, time must be subtracted:

11:15\text{ AM}

minus

3\text{ hours } 40\text{ minutes}

gives

07:35\text{ AM}

Step-by-Step Solution

Calculate the total longitudinal difference between City P (

40^\circ\text{E}

) and City Q (

15^\circ\text{W}

Longitudinal difference =

40^\circ + 15^\circ = 55^\circ

Since the two locations lie in different hemispheres (East and West), their longitudinal values must be added together to find total angular separation.

Convert the longitudinal difference into a time difference using the rate of

1^\circ = 4\text{ minutes}

Time difference =

55 \times 4\text{ minutes} = 220\text{ minutes} = 3\text{ hours } 40\text{ minutes}

The Earth rotates

360^\circ

in 24 hours, which corresponds to

15^\circ

per hour or

1^\circ

every 4 minutes.

Determine the local solar time at City Q by adjusting for directional orientation relative to City P.

11:15\text{ AM} - 3\text{ hours } 40\text{ minutes} = 07:35\text{ AM}

City Q is located to the west of City P, so its local time is behind (earlier than) City P.

Key Concept

Calculation of local solar time differences using longitudes across hemispheres

Estimated Time:1m 30s

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