This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

## Thursday, January 24, 2008

### Question on Phases of the Moon

In yesterday’s post, we created a 28-day chart in order to calculate the phases of the moon. In this post, we will apply what we have learnt to answer an actual Science question on phases of the moon.

Question

Rashid observed a full moon on 6 January. When will he most likely observe a full moon in February?

(1) 5 February
(2) 15 February
(3) 25 February
(4) 5 and 22 February

Using the 28-day chart, we count 28 days from 6 January.

28 + 6 = 34

Since January has 31 days, we minus 31 days.

34 – 31 ----> 3 February

Hence, Rashid would be likely to observe a full moon on 3 February. However, in the multiple choice question above, there is no 3 February. The closest date is 5 February. We therefore take the answer to be (1) 5 February.

Note: The answer (4) 5 and 22 February is not accepted because it takes 28 days for every full moon to appear and 22 February is only 17 days after 5 February.