A car during its journey travels 30 min at a speed of 40 km/h, another 45 min at a speed of 60 km/h and 2 h at a speed of 70 km/h. Find its average speed?

When N is a natural number, then there is only one possible case that N, N + 2, N + 4 are prime numbers.

When N = 3, then N, N + 2, N + 4 = 3, 5, 7 all are primes.

Let us assume the ratio product is Q.
According to question,
Quantity of Milk in mixture = 6Q ml
Quantity of Water in mixture = 2Q ml
Quantity of Milk in mixture + Quantity of Water in mixture = 640
6Q + 2Q = 640
8Q = 640
Q = 640/8
Q = 80
Quantity of Milk in mixture = 6Q ml = 6 x 80 = 480 ml
Quantity of Water in mixture = 2Q ml = 2 x 80 = 160 ml
To find the new mixture containing half milk and half water,
Quantity of water to be added for making the mixture of equal quantity of milk and water = 480 - 160 = 320

?DAC = ?B + ?C
(Exterior angle prop. of a ? ABC)
According to question,
130° = 2A + 3A
5A = 130°
A = 26°
? ?B = 52°; ?C = 78°

Total required marks in the three examinations = (3 x 600 x 70)/100 =1260

Marks secured in first examination = 55% of 600 = ( 600 x 55)/100 =330

Marks secured in second examination = 60% of 600 = ( 600 x 60)/100 =360

Thus, the required marks in third examination = 1260 - (330 + 360)
= 1260 - 690
= 570

Time taken by A to cover 400 m = Distance/ Speed
= 400/16 s = 25 s
? B covers (400 -16) = 384 m in(25 + 40) = 65 s
? B's speed = 384/65 =5.9 m/s

Probability of head or a tail on upper side of coin = 1/2
? Probability of getting same face on all three coins = 1/2 x 1/2 x 1/2
= 1/8

The distance covered by B in 35 seconds = 200 x 35 / 38 = 3500 / 19 m
Now, 200 ? 3500 / 19 = 300 / 19 = 15¹⁵?₁₉ m Hence, A can beat B by 15¹⁵?₁₉ m.