Solution 5

15 and 51 are not twin primes. Twin primes are a pair of primes that have a difference of 2. However, 15 is not a prime number, and the difference between 15 and 51 is not 2. So, the correct option would be “A is false but R is true.”

Solution 6

The least number that can be divided equally among 2, 3, 4, 5, 6, and 7 family members is 420. This is the least common multiple of these numbers.

Solution 7

a) If 30 students decide to go, the school will collect Rs 3000 less than the cost of 30 tickets. So, the school will need to collect Rs 2500 * 30 – Rs 3000 = Rs 72000.

b) Each student will pay Rs 72000 / 30 = Rs 2400.

c) The total cost of the diesel consumed will be Rs 95.50 * 15 = Rs 1432.50.

d) The bus will take 160 km / 40 km per hour = 4 hours.