CPhill

\($63\underline{\hphantom{0}}$ \)

If  this is  divisible  by  3, the  sum of its digits must also be divisible  by 3

The the possibilities for the units digit  are   0 , 3, 6  and  9

The  largest  difference is 9 - 0   =   9

We are asking ourselves  : 4%  of what =  1308  ???

.04  * what   = 1308        divide both sides by  .04

what  =  1308/.04  = 32700

Primes   = 10

One digit  = 3, 7

Two digit  =  13, 17, 37, 67, 73, 71, 61, 31

The number is  just  the sum of  the  first five triangular  numbers  = 

1  +  3  +  6  +  10  +  15   =

35

Note  that  the  area  of the square  = 4^2   = 16 cm^2

Triangles   ADM  and ABN  are  both  right.....their  combined  areas  = (2)(4)  =  8  cm^2

Triangle MNC is also right and has an area  =  (1/2)(2)(2)   =  2 cm^2

So....the area of triangle  AMN =   [16  -  8   -  2 ] cm^2    =   6  cm^2

8 + 1D   = 5D        where  D  is  the days we are looking for

Subtract 1D  from both sides

8 =  4D     divide both sides  by 4

2 = D

This  makes sense

Keenan sells  8 + 1*(2)  =  10  tubs  by the  end of  the second day

Chase sells  5(2)  = 10  tubs by the end of the second day

Sorry....I think  my fingers  hit  the wrong calculator keys....see  my corrected answer

Sometimes....I find  it  helpful  to  make  a chart

Call the people A, B, C, D

Cook                   Clean

AB                       CD

AC                       BD

AD                       BC

BC                       AD

BD                       AC

CD                       AD

This  makes  sense....from any  of the 4, we want to choose any 2 to  cook  = C(4,2)  = 6

The  ones  who clean  are  defaulted by our  choice  of the cooks

Thx, Cal   !!!!!

Average  =

[ 2*40 + 3*50  + 10*60 + 25*70  + 35*80  + 18*90 + 7*100 ]  / 100  =

[7700 ]  /  100  

77

CORRECTED