Find all multiples of 40 that lie between 310 and 410. Class 6

Find all multiples of 40 that lie between 310 and 410. Class 6

Question 1.

Find all multiples of 40 that lie between 310 and 410. Class 6

Solution:

All multiples of 40 lying between 310 and 410 are 320, 360 and 400. (40 × 8, 40 × 9, 40 × 10).

Question 2.

Who am I?

(а) I am a number less than 40. One of my factors is 7. The sum of my digits is 8. Class 6

(b) I am a number less than 100. Two of my factors are 3 and 5. One of my digits is 1 more than the other.

Solution:

(a) Number with one factor as 7 and less than 40 are 7, 14, 21, 28 and 35. Out of these numbers, sum of the digits of 35 is 3 + 5 = 8. So, I am 35.

(b) The numbers with factors 3 and 5 (i.e., multiples of 15) and less than 100 are 15, 30, 45, 60, 75 and 90.

In 45, digit 5 is 1 more than digit 4. So, I am the number 45.

Question 3.

A number for which the sum of all its factors is equal to twice the number is called a perfect number. The number 28 is a perfect number. Its factors are 1, 2, 4, 7, 14 and 28. Their sum is 56 which is twice 28. Find a perfect number between 1 and 10. Class 6

Solution:

Factors of 6 are 1, 2, 3 and 6. Also, sum of 1, 2, 3 and 6=l + 2 + 3 + 6 = 12, which is twice the number 6. So, 6 is the required perfect number between 1 and 10.