Ahmad opens up a magazine. The product of the page numbers which face him is 420. What pages is Ahmad looking at? Give your answers in the following format. (Eg 1, 2)
The page numbers must be one more than the other.
Left number = 1 u
Right number = 1 u + 1
Since the number ends with the digit 0, it is either a multiple of 5 or 10. We use the products of multiples of 10 to check.
10 x 10 = 100
20 x 20 = 400
30 x 30 = 900
40 x 40 = 1600
50 x 50 = 2500
60 x 60 = 3600
Since the product is 420, the product of the two page numbers is near to 400. One of the factors must be a multiple of 5 or 10.
Using guess and check,
19 x 20 = 380
20 x 21 = 420
Two pages that Ahmad is looking at: 20, 21
Answer(s): 20, 21
