I did my own calculation and got---->
The amount of fuel required to decelerate the Apollo 11 Command/Service Module (CSM) and Lander (L) after reaching the moon is calculated. The kinetic energy of Apollo 11 command-service module and lander (CSML) that is propagating to the moon is calculated using the distance to the moon (363,104,000 m) and the time that the Apollo 11 space craft (CSML) propagated to the moon (4 days 6 hours and 45 minutes [364,900 seconds]),
v = (distance)/(time) = (363,104,000 m)/(364,900 s) = 983 m/s.......................................................85
The total mass of the command, service modules and lander (CSML) is,
(CM) + (SM) + (L) = 5,560 kg + 24,520 kg + 16,400 kg = 49,480 kg................................................86
Using equations 85 an 86, the kinetic energy of the Apollo 11 CSML is calculated,
1/2 mv2 = (.5)(49,480 kg)(983 m/s)2 = 2.39 x 1010 J.........................................................................87
Using the kinetic energy of the CSML (equ 87) and the energy of a kilogram of rocket fuel (4.2 x 107 J/kg), the minimum amount of fuel required to decelerate the CSML is calculated,
Fuel mass = (KE)/(fuel energy) = (2.39 x 1010 J)/(4.2 x 107 J/kg) = 569 kg...................................88
Using the rocket engine efficiency of 1% and the result of equation 88,
(569 kg)/X = .01 -------------> X = 56,900 kg......................................................................................89