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diff --git a/698/CH18/EX18.5/P5_lewis_equation.sce b/698/CH18/EX18.5/P5_lewis_equation.sce
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+++ b/698/CH18/EX18.5/P5_lewis_equation.sce
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+clc
+//Example 18.5
+//Design using lewis equation
+
+P=5e3
+N=900
+phi=20
+G=3
+//Assuming a standard module of 1 mm
+m=1
+
+Dp=80
+Np=Dp/m
+Sp=200e6
+
+Ng=G*Np
+Dg=m*Ng
+Sg=150e6
+
+printf('A standard module of 1 mm has been assumed.\n')
+printf('Based on the number of teeth of gear and pinion, and the corresponding form factors, gear is weaker.\n')
+printf('\typ=0.139 \t Syp=200*0.139 =27.8 \n\tyg=0.148 \t Syg=150*0.148 =22.2 \n\n')
+
+Mt=(P*60)/(2*%pi*N)
+F=(2*Mt)/(Dp*1e-3)
+yg=0.148
+k=4
+
+//Putting the value of yg in Lewis Equation
+m_new=sqrt(F/(Sg*k*(%pi^2)*yg))
+printf('The revised module is %0.3f mm\n',m_new*1e3)
+printf('Taking a standard module of 1.25 mm,\n')
+m_new=1.25
+
+Np=Dp/m_new
+Ng=Dg/m_new
+
+printf('New number of teeth:\n\tNp=%d\typ=0.135 and\n\tNg=%d\tyg=0.147\n\n',Np,Ng)
+printf('Using the new module in lewis equation to check for safety:\n')
+//Using the m_new in the lewis equation to check for safety,
+aa=1/((m_new^2)*0.147)
+bb=(Sg*k*(%pi^2))/F
+
+if aa<bb
+   printf('The design is safe\n\n')
+else
+   printf('The design will fail\n\n')
+end
+
+//Face width
+b=k*%pi*m_new
+printf('Face width of gear is %0.3f mm\n',b)
+printf('The width is standardized to 16 mm')
+
+//End of programme
+\ No newline at end of file