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primary 5 | Maths
| Whole Numbers
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Hi. Pls help with this question ASAP. Thanks
Date Posted: 3 years ago
Views: 250
In each case, the number needs to increase by 2 to have no remainder.
This is because 1 + 2 = 3 while 3 + 2 = 5.
So, if the number is increased by 2, it will be exactly divisible by 3 and by 5, so the new number will be a multiple of 3 and of 5.
The smallest of these is 15.
So, the number we are looking for is 15 - 2, or 13.
This is because 1 + 2 = 3 while 3 + 2 = 5.
So, if the number is increased by 2, it will be exactly divisible by 3 and by 5, so the new number will be a multiple of 3 and of 5.
The smallest of these is 15.
So, the number we are looking for is 15 - 2, or 13.
P5 heuristic method : Listing
From the question info, we can say that :
Number = 3 × _ + 1
(Multiple of 3 , plus 1 more)
And :
Number = 5 × _ + 3
(Multiple of 5, plus 3 more)
What we do not know are the numbers in the blanks.
① List the multiples of 3. Then add 1 to them to get the possible numbers.
3,6,9,12,15,18,21,24,27,30,...
↓
4,7,10,13,16,19,22,25,28,31,...
② List the multiples of 5. Then add 3 to them to get the possible numbers.
5,10,15,20,25,30,...
↓
8,13,18,23,28,33,...
We see that 13 and 28 are in both rows. So they satisfy the question information and are possible answers.
28 ÷ 3 = 9 R1 → 28 = 9 x 3 + 1
28 ÷ 5 = 5 R3 → 28 = 5 x 5 + 3
13 ÷ 3 = 4 R1 → 13 = 4 x 3 + 1
13 ÷ 5 = 2 R3 → 13 = 2 x 5 + 3
Since question asks for smallest possible number, the answer is 13.
From the question info, we can say that :
Number = 3 × _ + 1
(Multiple of 3 , plus 1 more)
And :
Number = 5 × _ + 3
(Multiple of 5, plus 3 more)
What we do not know are the numbers in the blanks.
① List the multiples of 3. Then add 1 to them to get the possible numbers.
3,6,9,12,15,18,21,24,27,30,...
↓
4,7,10,13,16,19,22,25,28,31,...
② List the multiples of 5. Then add 3 to them to get the possible numbers.
5,10,15,20,25,30,...
↓
8,13,18,23,28,33,...
We see that 13 and 28 are in both rows. So they satisfy the question information and are possible answers.
28 ÷ 3 = 9 R1 → 28 = 9 x 3 + 1
28 ÷ 5 = 5 R3 → 28 = 5 x 5 + 3
13 ÷ 3 = 4 R1 → 13 = 4 x 3 + 1
13 ÷ 5 = 2 R3 → 13 = 2 x 5 + 3
Since question asks for smallest possible number, the answer is 13.
See 1 Answer
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For this qn u need to know the multiples of 3: so 3,6, 9,12...
since the remainder is 1, the possible numbers will be 4,7,10,13...
multiples of 5 are: 5,10,15, 20
since remainder is 3, possible numbers are: 8,13....
for smallest possible number just find the smallest number that matches both, so the ans = 13
since the remainder is 1, the possible numbers will be 4,7,10,13...
multiples of 5 are: 5,10,15, 20
since remainder is 3, possible numbers are: 8,13....
for smallest possible number just find the smallest number that matches both, so the ans = 13
Date Posted:
3 years ago
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