72 persons have enough food for 7 days . but after one day they decided to finish the food in 3 remaining days . For if they invited more persons how many persons did they invite?

We have been given that

72 persons has enough food for 7days.

After 1 day they decided to finish the food in remaining 3 days.

We need to find number of invitees to finish the food.

After one day there are 72 people and they have food for 6 days.

If people are changed n times, time will change to (1/n) of initial time.

\frac{1}{n}\times 6\ =\ 3n1×6 = 3

Therefore n = 2

Total number of people needed  = n × 72

Total number of people needed = 72×2

Total number of people needed  = 144

Hence the number of invitees = 144 - 72 =72

72 people are invited to finish the food in 3 days

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.