Q8)
If c + d = 11 and c and d are positive integers, which of the following is a possible value for 5c + 8d?
- 55
- 61
- 69
- 83
- 88
The explanation at the back offered two approaches. I understand the first one but don't understand the second:
...you can notice that consecutive values of 5c + 8d differ by 3. In other words, every possible value of 5c + 8d equals a multiple of 3 plus some constant...
Question one: what is the rule here? What happens when a Multiple of 5, MO5, is added to a Multiple of 8, MO8? (I tried looking in the number properties book and found nothing)
I've also tried working this relationship out with numbers and found that if c & d in the above equation is different then the resulting number isn't a MO3. However, if c=d then the result is MO3 + some constant.
Can someone show me the light?
Thank you in advance.
If c + d = 11 and c and d are positive integers, which of the following is a possible value for 5c + 8d?
- 55
- 61
- 69
- 83
- 88
The explanation at the back offered two approaches. I understand the first one but don't understand the second:
...you can notice that consecutive values of 5c + 8d differ by 3. In other words, every possible value of 5c + 8d equals a multiple of 3 plus some constant...
Question one: what is the rule here? What happens when a Multiple of 5, MO5, is added to a Multiple of 8, MO8? (I tried looking in the number properties book and found nothing)
I've also tried working this relationship out with numbers and found that if c & d in the above equation is different then the resulting number isn't a MO3. However, if c=d then the result is MO3 + some constant.
Can someone show me the light?
Thank you in advance.
