The cost of posting one inland letter is 5k and one overseas letter is 10k. A messenger spent N1.20 in posting 4 overseas letters and some inland letters. How many inland letters did he post?
Show workings
To find out how many inland letters the messenger posted, we need to calculate the cost of posting the overseas letters and subtract it from the total amount spent.
First, let's calculate the total cost of posting the 4 overseas letters:
Cost of one overseas letter = 10k
Total cost of 4 overseas letters = 4 * 10k = 40k
Next, we subtract the cost of the overseas letters from the total amount spent (N1.20):
Total amount spent - Cost of overseas letters = Cost of inland letters
N1.20 - 40k = Cost of inland letters
Since we can't directly subtract the cost of the overseas letters from N1.20 (as they have different units), let's convert the cost of the overseas letters to Naira.
1k = N0.001
Cost of overseas letters = 40k * N0.001 = N0.04
Now, we can finally calculate the cost of the inland letters:
Total amount spent - Cost of overseas letters = Cost of inland letters
N1.20 - N0.04 = Cost of inland letters
N1.16 = Cost of inland letters
The cost of posting one inland letter is 5k in Naira. Therefore, to find out how many inland letters the messenger posted, we divide the cost of the inland letters by the cost of posting one inland letter:
Number of inland letters = Cost of inland letters / Cost of posting one inland letter
Number of inland letters = N1.16 / 5k
To calculate this, let's convert the cost of the inland letters to kobo:
1 Naira = 100 kobo
Cost of inland letters = N1.16 * 100 = 116 kobo
Number of inland letters = 116 kobo / 5k
Now let's convert kobo to Naira:
1k = N0.001
116 kobo = 116 * N0.001 = N0.116
Number of inland letters = N0.116 / 5k
To calculate the value:
1k = N0.001
Number of inland letters = N0.116 / 0.005 = 23.2
Since we can't have a fraction of a letter, we round down to the nearest whole number.
Therefore, the messenger posted 23 inland letters.