Grace's exercise programme requires that she does 1 sit-up on the first day, 2 sit-ups on the second day, 6 sit-ups on the third day, 15 sit-ups one the fourth days and so on until she does at least 50 sit-ups each day. How many days must Grace exercise to reach her
target of 50 sit-ups per day?

sorry it is hard little

i do not want to give you wrong answer sorry

Step-by-step explanation:

where's the diagrams?

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4