Answer
Find out the what is the surface area of the pyramid .
To proof
Formula
Surface area of a square pyramid

Where a is the base edge and h be the height .
As given
A square pyramid has a base with side lengths each measuring 40 inches. The pyramid is 21 inches tall, with a slant height of 29 inches.
i.e Base edge = 40 inches
Height = 21 inches
Put values in the above formula

solving



= 1600 + 80 × 29
= 3920 inches²
Therefore the surface area of the pyramid is 3,920 inches²
Hence proved
11 1/8
Explanation
The answer comes out to 11.125 however in mixed number form it’s 11 1/8
Answer:
To make 65 chocolate drinks, she needs:
12 g of chocolate powder and 5 marshmallows per drink.
Then she needs:
12g*65 = 780 grams of chocolate powder.
We know that the chocolate powder comes in jars of 250g, such that each one costs £2.99
If she buys 3 jars, she will have: 3*250g = 750g
So she will not have enough, then she needs to buy 4 jars.
Then in chocolate powder, she will pay 4 times £2.99 = £11.96
And for marshmallows, she needs:
65*5 = 325 in total.
Marshmallows come in bags of 120, then the number of packs that Abi needs to buy is:
325/120 = 2.7
That should be rounded up (because she can not buy a 0.7 of a bag)
Then she needs 3 bags, and each bag costs £1.45
Then the total cost in marshmallows is 3*£1.45 = £4.35