# Khan/khan-exercises

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 Adding and subtracting mixed numbers with unlike denominators
randRangeNonZero( -1, 1 ) ( PM === 1 ? "+" : "-") randRange( 2, 19 ) ( PM === 1 ? randRange( 1, 19 ) : randRange( -W1 + 1, -1 ))
randRange( 3, 20 ) randRange( 3, 20 )
randRange( 1, D1 - 1 ) randRange( 1, D2 - 1 )
getGCD( N1, D1 ) N1 / GCD1 D1 / GCD1 getGCD( N2, D2 ) N2 / GCD2 D2 / GCD2 getLCM( SIMP_D1, SIMP_D2 ) getGCD( SIMP_N1 * LCM / SIMP_D1 + PM * SIMP_N2 * LCM / SIMP_D2 , LCM )

expr(["+", W1 + fraction( N1, D1 ), W2 + fraction( N2, D2 )]) = {?}

W1 + W2 + N1 / D1 + PM * N2 / D2

Separate the whole numbers from the fractional parts:

= \blue{W1} + \blue{fraction( N1, D1 )} SIGN \pink{abs( W2 )} SIGN \pink{fraction( N2, D2 )}

Bring the whole numbers together and the fractions together:

= \blue{W1} SIGN \pink{abs( W2 )} + \blue{fraction( N1, D1 )} SIGN \pink{fraction( N2, D2 )}

=W1 + W2 + \blue{fraction( N1, D1 )} SIGN \pink{fraction( N2, D2 )}

Simplify each fraction:

= W1+W2 + \blue{fraction( SIMP_N1, SIMP_D1 )} SIGN \pink{fraction( SIMP_N2, SIMP_D2 )}

Find a common denominator for the fractions:

= expr(["+", W1 + W2, fraction( SIMP_N1 * LCM / SIMP_D1, LCM ),fraction( PM * SIMP_N2 * LCM / SIMP_D2, LCM )])

= expr(["+", W1 + W2, fraction( SIMP_N1 * LCM / SIMP_D1 + PM * SIMP_N2 * LCM / SIMP_D2, LCM )])

Combine the whole and fractional parts into a mixed number:

= W1 + W2 + fraction( SIMP_N1 * LCM / SIMP_D1 + PM * SIMP_N2 * LCM / SIMP_D2, LCM )

Simplify to lowest terms:

= W1 + W2 + fractionReduce( SIMP_N1 * LCM / SIMP_D1 + PM * SIMP_N2 * LCM / SIMP_D2, LCM )

-1 "-" randRange( 2, 19 ) randRange( -W1 + 1, -1 )
randRange( 3, 20 ) randRange( 3, 20 )
randRange( 1, D1 - 1 ) randRange( 1, D2 - 1 )
getGCD( N1, D1 ) N1 / GCD1 D1 / GCD1 getGCD( N2, D2 ) N2 / GCD2 D2 / GCD2 getLCM( SIMP_D1, SIMP_D2 ) getGCD( SIMP_N1 * LCM / SIMP_D1 + PM * SIMP_N2 * LCM / SIMP_D2 , LCM )

expr(["+", W1 + 1 + fraction( N1, D1 ), W2 + fraction( N2, D2 )]) = {?}

W1 + 1 + W2 + N1 / D1 + PM * N2 / D2

Simplify each fraction.

= \blue{W1 + 1fraction( SIMP_N1, SIMP_D1 )} SIGN \pink{abs( W2 )fraction( SIMP_N2, SIMP_D2 )}

Find a common denominator for the fractions:

= \blue{W1 + 1fraction( SIMP_N1 * LCM / SIMP_D1, LCM )}SIGN\pink{abs( W2 )fraction( SIMP_N2 * LCM / SIMP_D2, LCM )}

Convert \blue{W1 + 1fraction( SIMP_N1 * LCM / SIMP_D1, LCM)} to \blue{ W1 + fraction( LCM, LCM) + fraction( SIMP_N1 * LCM / SIMP_D1, LCM)}.

So the problem becomes:

\blue{W1fraction( LCM + SIMP_N1 * LCM / SIMP_D1, LCM)}SIGN\pink{abs( W2 )fraction( SIMP_N2 * LCM / SIMP_D2, LCM)}

Separate the whole numbers from the fractional parts:

= \blue{W1} + \blue{fraction( LCM + SIMP_N1 * LCM / SIMP_D1, LCM )} SIGN \pink{abs( W2 )} SIGN \pink{fraction( SIMP_N2 * LCM / SIMP_D2, LCM)}

Bring the whole numbers together and the fractions together:

= \blue{W1} SIGN \pink{abs( W2 )} + \blue{fraction( LCM + SIMP_N1 * LCM / SIMP_D1, LCM )} SIGN \pink{fraction( SIMP_N2 * LCM / SIMP_D2, LCM )}

=W1 + W2 + \blue{fraction( LCM + SIMP_N1 * LCM / SIMP_D1, LCM )} SIGN \pink{fraction( SIMP_N2 * LCM / SIMP_D2, LCM)}